Coots Soil - K Deficiency in flower

perilousp · Dec 15, 2025

Hi guys,

First time posting here, so hello!

Ive got a decent number of grows under my belt, both indoor and outdoor.

My current setup is a multistrain (all from seed) - Bruce banner, Blackberry Moonrocks, GG#4, and CBD Lemon Auto.

All plants are in a 4x4 tent, with 550w full spec LEDs. Watered with low tds water, with fresh aloe vera. Occasionally added in fresh moringa leaf blend and seaweed extract. Top dressed with vermicompost twice now (we are currently 26 days since 12-12 flip).

Veg phase went amazingly well, all plants were deep green, lush, large, upright. I trained them pretty well. Moonrocks was slightly stunted early on due to water logging, so lagged in pace and size, but looked stunning once it recovered - picture perfect. CBD Lemon Auto was transplanted in about two weeks later than the three photos - but is still about two weeks ahead (via pistil sightings).

Around week 2 of flower (for photos), the tips of moonrocks started getting light. Slowly what seemed like a K deficiency started taking over - tips and leaf margins lightening, and eventually turning brown and crispy. The same issue was plaguing CBD Lemon Auto.

Given the soil is the same - well cooked for about 6 weeks - for all species, and the significantly larger Brucer Banner and GG#4 showed no such deficiency, i’m wondering whether it’s an issue of low water cycling in the smaller plants. Where GG and Banner tear through a litre per day, moonrocks and cbd barely consume 200ml per day - ive been weighing the pots with a commercial scale i had lying around.

Even so, the deficiency is slowly spreading. CBD looks awful, and the once beautiful Moonrocks is slowly following suit. Id love some insights from you guys as to what this could be.

PPFD (plant heights adjusted for target ppfds):
- Banner & GG#4: 650-800
- Moonrocks: 600-700
- CBD Lemon Auto: 500-600

Temps: 25-27 C (day), 22-23 C (night)
RH: 50-55% (day), 50-58% (night)

Watering cycle:
Banner & GG#4 - 1.5 litres each every 24-36h
Moonrocks: 1 litre appx every 48-72 hours
CBD: Whenever weight drops by 1kg from field capacity

Photos Attached:
1-2: BB Moonrocks
3-4: GG#4
5-6: Bruce Banner
7-9: CBD Lemon Auto

Jez187 · Dec 15, 2025

whats your ph when feeding?

perilousp · Dec 15, 2025

Btw CBD and Moonrocks may look slightly wet in parts because I had foliar sprayed very low dose Potassium Sulphate. The foliar seems to have helped somewhat, that is new sugar leaves look fine, but the older leaves are still progressing in their crisping.

perilousp · Dec 15, 2025

Jez187 said:
whats your ph when feeding?

Hey Jez, PH is about 6.2-6.5. I use 20 litre bottled water cans, because our ground/tap water here is ridiculously alkaline (8-9).

The bottled water is filtered of particulates, contaminants etc, and sterilized. I believe they also add back some calcium and magnesium post filtration - as per their website.

perilousp · Dec 15, 2025

One more thing. It’s coots mix, but I used buffered cocopeat in place of peat moss (due to availability in my region). I bought low EC coco, washed it, and buffered it myself with calcium and magnesium.

Just in case that could be a potential contributor to the issues im seeing.

Jez187 · Dec 15, 2025

perilousp said:
Hey Jez, PH is about 6.2-6.5. I use 20 litre bottled water cans, because our ground/tap water here is ridiculously alkaline (8-9).

The bottled water is filtered of particulates, contaminants etc, and sterilized. I believe they also add back some calcium and magnesium post filtration - as per their website.

I grow in coco coir and have to have my ph at 5.8.

perilousp said:
Hi guys,

First time posting here, so hello!

Ive got a decent number of grows under my belt, both indoor and outdoor.

My current setup is a multistrain (all from seed) - Bruce banner, Blackberry Moonrocks, GG#4, and CBD Lemon Auto.

All plants are in a 4x4 tent, with 550w full spec LEDs. Watered with low tds water, with fresh aloe vera. Occasionally added in fresh moringa leaf blend and seaweed extract. Top dressed with vermicompost twice now (we are currently 26 days since 12-12 flip).

Veg phase went amazingly well, all plants were deep green, lush, large, upright. I trained them pretty well. Moonrocks was slightly stunted early on due to water logging, so lagged in pace and size, but looked stunning once it recovered - picture perfect. CBD Lemon Auto was transplanted in about two weeks later than the three photos - but is still about two weeks ahead (via pistil sightings).

Around week 2 of flower (for photos), the tips of moonrocks started getting light. Slowly what seemed like a K deficiency started taking over - tips and leaf margins lightening, and eventually turning brown and crispy. The same issue was plaguing CBD Lemon Auto.

Given the soil is the same - well cooked for about 6 weeks - for all species, and the significantly larger Brucer Banner and GG#4 showed no such deficiency, i’m wondering whether it’s an issue of low water cycling in the smaller plants. Where GG and Banner tear through a litre per day, moonrocks and cbd barely consume 200ml per day - ive been weighing the pots with a commercial scale i had lying around.

Even so, the deficiency is slowly spreading. CBD looks awful, and the once beautiful Moonrocks is slowly following suit. Id love some insights from you guys as to what this could be.

PPFD (plant heights adjusted for target ppfds):
- Banner & GG#4: 650-800
- Moonrocks: 600-700
- CBD Lemon Auto: 500-600

Temps: 25-27 C (day), 22-23 C (night)
RH: 50-55% (day), 50-58% (night)

Watering cycle:
Banner & GG#4 - 1.5 litres each every 24-36h
Moonrocks: 1 litre appx every 48-72 hours
CBD: Whenever weight drops by 1kg from field capacity

Photos Attached:
1-2: BB Moonrocks
3-4: GG#4
5-6: Bruce Banner
7-9: CBD Lemon Auto

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looks like nutrient lockout to me salt build up ph to high possibly? whats the run off ph saying? is say overfed ph drifting high nute lock but just my opinion I'd flush them correct ph and reduced feed maybe

perilousp · Dec 15, 2025

Jez187 said:
I grow in coco coir and have to have my ph at 5.8.

looks like nutrient lockout to me salt build up ph to high possibly? whats the run off ph saying? is say overfed ph drifting high nute lock but just my opinion I'd flush them correct ph and reduced feed maybe

Hey Jez,

Nute lockout in a decently aged coots living soil? I thought the idea of such soils was to buffer against nutrient spikes via the symbiosis of plant roots and microbes.

I’ll check the runoff PH, but again, I was under the impression that a living soil like this should buffer against ph spikes, though always happy to be taught a little more!

Just to clarify, i don’t use any nutrients at all. Only aloe vera with plain water, and the occasional vermicompost top dress and some seaweed extract (though very little and rarely, can’t imagine it would cause salt buildup?) .

Jez187 · Dec 15, 2025

perilousp said:
Hey Jez,

Nute lockout in a decently aged coots living soil? I thought the idea of such soils was to buffer against nutrient spikes via the symbiosis of plant roots and microbes.

I’ll check the runoff PH, but again, I was under the impression that a living soil like this should buffer against ph spikes, though always happy to be taught a little more!

Just to clarify, i don’t use any nutrients at all. Only aloe vera with plain water, and the occasional vermicompost top dress and some seaweed extract (though very little and rarely, can’t imagine it would cause salt buildup?) . ye Im not sure the sorry i know seaweed extract has alot of nitrogen and I wouldn;t use during flower only veg myself. I grow with complete diffrent method soz hope you figure it out x

GNick55 · Dec 15, 2025

light stress

perilousp · Dec 15, 2025

GNick55 said:
light stress

Hey there. Could you please elaborate? I though the PPFD was quite low for week 4 of flower for the two afflicted plants.

GNick55 · Dec 15, 2025

perilousp said:
Hey there. Could you please elaborate? I thought the PPFD was quite low for week 4 of flower for the two afflicted plants.

ok, i just went back and re read everything,. let’s start with watering?
you water daily because there’s coco in the medium? among with soil as well? two things watering that often can cause problems, also everytime you water them that soil is releasing nutrients,. how and why do you water everyday? explain your technique

perilousp · Dec 15, 2025

GNick55 said:
ok, i just went back and re read everything,. let’s start with watering?
you water daily because there’s coco in the medium? among with soil as well? two things watering that often can cause problems, also everytime you water them that soil is releasing nutrients,. how and why do you water everyday? explain your technique

Hey there,

So I haven’t been watering daily. Till recently, waterings tended to be approximately 3-4 days apart. I experimented, trying to observe the plants, even started weighing the pots at one point. Even now, I water only GG and Banner once every 36 hours or so. I started weighing them, and GG and Banner lose about 1kg / 1 litre per day roughly. I water them when I notice their normally praying leaves begin to droop.

Moonrocks and CBD on the other hand don’t give any such visual indication, they remain praying pretty much all the time. I just notice this seeming K deficiency spread.

I think I did overwater moonrocks and cbd at some point, when i kept them in the same watering cycle as GG and Banner briefly. I think this happened in very early veg, and then once just before flip. Now I try to wait till they’ve lost about 1.5kg via transpiration etc. I’m basically still unsure how to gauge when those two need water.

perilousp · Dec 15, 2025

GNick55 said:
ok, i just went back and re read everything,. let’s start with watering?
you water daily because there’s coco in the medium? among with soil as well? two things watering that often can cause problems, also everytime you water them that soil is releasing nutrients,. how and why do you water everyday? explain your technique

Also to give you a better picture, it’s basically coots soil mix, but I substituted cocopeat (mg and ca buffered) for the peat moss portion. I also added some charged biochar (charged with homemade compost and some vermi).

I water using a 4 litre watering can. Add in about 10 ml fresh aloe vera juice, Aerate for 20 mins, and water in rings till slight runoff.

A day or so after flip, I added about an inch of store bought vermicompost, because we ran out of home made (winter). Unfortunately all store bought vermi around here is cow dung based. I noticed it tended to form a hard layer after watering that needed to be broken up. Problems seemed to take off after this point id say.

Mulched the pots two weeks ago as the top soil was drying quicker than the bottom sometimes - in moonrocks and cbd only. I wonder if this only made things worse.

stanknkatz · Dec 16, 2025

Sounds to me like he's growing in coco amended with worm castings and whatever else is in coots mix. He'd have been better off just going with straight coco. Coco is not peat moss and you can't treat it the same.

perilousp · Dec 17, 2025

stanknkatz said:
Sounds to me like he's growing in coco amended with worm castings and whatever else is in coots mix. He'd have been better off just going with straight coco. Coco is not peat moss and you can't treat it the same.

You’re right, it isn’t the same. And this is an issue ive run into before using coco + compost + aeration + amendments. Despite this, I have managed good yields and quality in the past. With unbuffered coco, i would have all kinds of issues - especially mg. With buffered, it generally seems localised to K deficiency in flower.

It’s also a case of regional availability, and working with what you have. I do believe this system can be improved to counter for such things, but that is my learning and of course, im reaching out to see if more experienced growers might have valuable inputs on this.

Now I know mg and ca dominate cec preference in coco, pushing out K in the buffering process. What im thinking is, perhaps some regular potassium sulphate in my water could help with this? If anyones familiar with this type of grow, id really appreciate any inputs!

GNick55 · Dec 17, 2025

perilousp said:
You’re right, it isn’t the same. And this is an issue ive run into before using coco + compost + aeration + amendments. Despite this, I have managed good yields and quality in the past. With unbuffered coco, i would have all kinds of issues - especially mg. With buffered, it generally seems localised to K deficiency in flower.

It’s also a case of regional availability, and working with what you have. I do believe this system can be improved to counter for such things, but that is my learning and of course, im reaching out to see if more experienced growers might have valuable inputs on this.

Now I know mg and ca dominate cec preference in coco, pushing out K in the buffering process. What im thinking is, perhaps some regular potassium sulphate in my water could help with this? If anyones familiar with this type of grow, id really appreciate any inputs!

it’s not about more experienced growers it’s you made it way more complicated than need be,..

perilousp · Dec 17, 2025

Could you elaborate? In the asian subcontinent, peat moss is not readily available. Cocopeat is. What would you suggest?

amneziaHaze · Dec 18, 2025

perilousp said:
Btw CBD and Moonrocks may look slightly wet in parts because I had foliar sprayed very low dose Potassium Sulphate. The foliar seems to have helped somewhat, that is new sugar leaves look fine, but the older leaves are still progressing in their crisping.

How does potassium sulfate taste when you smoke it?
Did you see ph after nute mix with tap water? Usually it drops down after nutes

perilousp · Dec 19, 2025

Right, well thank you for all the helpful replies my friends. I’ll figure it out on my own.

Ninjadogma · Dec 19, 2025

perilousp said:
Right, well thank you for all the helpful replies my friends. I’ll figure it out on my own.

When you throw it out there and get 20 different "expert" opinions, at least you can say you sought feedback.

Just peeked at your photos at the top. I think you are just running the lights a little bright on the plants and it's triggering the deficiency you're seeing.

Why?

Take a look at where your tips are burning. It's toward the top of the plant. If you look lower, those tips aren't burnt. Yes it's a growing deficiency and yeah we can see you're losing potassium along the margens, but the lightened leaf pleats suggest you've got mag stripping going on and thats a classic sign the lights are too strong.

If you have a dimmer and you're running 100%, dial it down to about 75% output. If no dimmer, raise the light by about 6 inches. Then keep an eye on it for a few days, it should stop the progression.

Lately I've been seeing a lot of salt and watering issues on the forums, but yours just looks like a real easy fix with the light.

Edit: Stand by, just looked at more of your photos, you've got more than one problem.

Coots Soil - K Deficiency in flower

Coots Soil - K Deficiency in flower

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Jez187

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GNick55

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stanknkatz

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