Coots Soil - K Deficiency in flower

Ninjadogma · Dec 19, 2025

Ninjadogma said:
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.

Do you have any inkling as to where your EC is sitting? You're right, there's an issue with potassium but it could be an over or an under. If you have low EC, feed. If it's high and you're questioning whether that high number includes the potassium it needs, you can dilute it down to a lower number and then put together a feeding that pushes a better ratio and guarantees the potassium placement. This is one of the pluses of hybrid feeding, you can steer the ratio as needed and more easily make necessary corrections. Of course, it's also easier to screw up too.

perilousp · Dec 20, 2025

Ninjadogma said:
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.

Hey thanks for that Ninjadogma, appreciate the constructive feedback.

I had a feeling it could have been the lights. The biggest plants are at about 600-750 ppfd, smaller ones are closer to 500-650. I had lowered the lights about a week or so ago to bring it to these figures, and yes, that accelerated the minor issues I was seeing before.

A case of the increased light pushing the root + nutrient cycling + delivery systems past their capacity?

You mentioned you noticed more than one problem. Could you elaborate please?

Again, thank you for the genuinely helpful feedback. Will tone down the lights slightly for starters.

perilousp · Dec 20, 2025

Ninjadogma said:
Do you have any inkling as to where your EC is sitting? You're right, there's an issue with potassium but it could be an over or an under. If you have low EC, feed. If it's high and you're questioning whether that high number includes the potassium it needs, you can dilute it down to a lower number and then put together a feeding that pushes a better ratio and guarantees the potassium placement. This is one of the pluses of hybrid feeding, you can steer the ratio as needed and more easily make necessary corrections. Of course, it's also easier to screw up too.

So I don’t have an EC measure directly, but TDS in my water supply is about 120-150, so pretty low. Most waterings have been just water + aloe. Sometimes I add in some seaweed extract which would raise the TDS slightly. And then recently I added in the Potassium Sulphate at 1g/litre, which again I assume would raise it a bit. But symptoms were clear and present already before I used the potassium sulphate.

Ninjadogma · Dec 20, 2025

perilousp said:
So I don’t have an EC measure directly, but TDS in my water supply is about 120-150, so pretty low. Most waterings have been just water + aloe. Sometimes I add in some seaweed extract which would raise the TDS slightly. And then recently I added in the Potassium Sulphate at 1g/litre, which again I assume would raise it a bit. But symptoms were clear and present already before I used the potassium sulphate.

It's what you previously fed I'm worried about.

perilousp · Dec 20, 2025

Ninjadogma said:
It's what you previously fed I'm worried about.

In terms of nutrients? I haven’t used any. Just a couple of top dressings over the so far 12 weeks - earthworm castings, sprouted millet flour.

In terms of watered-in nutrition, as i mentioned - seaweed extract, potassium sulphate (only very recently), epsom salts in low doses probably twice, and aloe vera.

Ninjadogma · Dec 20, 2025

perilousp said:
In terms of nutrients? I haven’t used any. Just a couple of top dressings over the so far 12 weeks - earthworm castings, sprouted millet flour.

In terms of watered-in nutrition, as i mentioned - seaweed extract, potassium sulphate (only very recently), epsom salts in low doses probably twice, and aloe vera.

Youre making an argument that it's starving, so just go ahead and feed it. Full dose too. If you're wrong, we can start a new conversation. Or you can invest the $10 for an EC pen and find out what's really going on before you make a move. Up to you.

Here's the problem. I'm saying plant looks burnt. What you are describing as a feed would suggest it's severely malnourished. Both can look similar. So if you're sure you haven't given them anything that would have spiked the nutrient load, they need to be fed. And if you're wrong and something in there was going nuclear, then you've just made it exponentially worse. See why I want you to gather data?

perilousp · Dec 21, 2025

Ninjadogma said:
Youre making an argument that it's starving, so just go ahead and feed it. Full dose too. If you're wrong, we can start a new conversation. Or you can invest the $10 for an EC pen and find out what's really going on before you make a move. Up to you.

Here's the problem. I'm saying plant looks burnt. What you are describing as a feed would suggest it's severely malnourished. Both can look similar. So if you're sure you haven't given them anything that would have spiked the nutrient load, they need to be fed. And if you're wrong and something in there was going nuclear, then you've just made it exponentially worse. See why I want you to gather data?

Understood. EC meter should be in tomorrow. Will check the water as well as the runoff and get back to you. Thanks!

Ninjadogma · Dec 21, 2025

perilousp said:
Understood. EC meter should be in tomorrow. Will check the water as well as the runoff and get back to you. Thanks!

Awesome. How is it doing right now? It's been a week since you uploaded the photos. Can you snap an updated pic? That may or may provide us with some insight based on how it has progressed.

perilousp · Dec 22, 2025

Symptoms have definitely progressed since then. A week ago, there were no real symptoms on the big boys GG#4 and Bruce Banner.

There are now. GG#4 more pronouncedly, and Banner minor.

BB Moonrocks:

GG#4:

CBD Lemon Auto:

Bruce Banner:

Fryer420 · Dec 22, 2025

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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if you look the lower on the plant the worse it got, it seems to be growing out of it, the tops are less damaged, think back what you did about a week ago and dont do it again lol , maybe when you sprayed the lights came on prior to it all being able soak up or evaporate and you burnt your plants a bit ,

perilousp · Dec 22, 2025

Fryer420 said:
if you look the lower on the plant the worse it got, it seems to be growing out of it, the tops are less damaged, think back what you did about a week ago and dont do it again lol , maybe when you sprayed the lights came on prior to it all being able soak up or evaporate and you burnt your plants a bit ,

Wish that were the case, but it has got worse. The increased lower damage may just be due to it being a mobile nutrient issue.

Ninjadogma · Dec 22, 2025

perilousp said:
Wish that were the case, but it has got worse. The increased lower damage may just be due to it being a mobile nutrient issue.

Despite what little you say you fed them, they're exhibiting symptoms of potassium burn and magnesium lockout. Potassium when deficient doesn't burn edges. It specifically does that in excess. The pleats getting lighter is magnesium lockout and it's what you will also expect to see when there's way too much potassium.

perilousp · Dec 22, 2025

Ninjadogma said:
Despite what little you say you fed them, they're exhibiting symptoms of potassium burn and magnesium lockout. Potassium when deficient doesn't burn edges. It specifically does that in excess. The pleats getting lighter is magnesium lockout and it's what you will also expect to see when there's way too much potassium.

This is Moonrocks ^ 3 weeks ago. No trouble at all, and also no nutrition either. The issues started cropping up as peak K demand started coming in.

Same with CBD Lemon Auto here:

Now, as far as what I know of cocopeat, unwashed / unbuffered coco will have an excess of K and Sodium. But it was washed, and buffered. In this case, the K and Sodium are knocked out of the Cation Exchange Sites, and Mg and Calcium take their spots.

My water does have Calcium and magnesium in it - as per bottler’s specs. But very little potassium.

But as I mentioned, the potassium sulphate was the first bit of “nutrient feeding” the plants got, and that was only after symptoms were becoming alarming. The goal was to have a “just water” grow (with a couple of compost top ups) using a modified coots mix

Ninjadogma · Dec 22, 2025

perilousp said:
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This is Moonrocks ^ 3 weeks ago. No trouble at all, and also no nutrition either. The issues started cropping up as peak K demand started coming in.

Same with CBD Lemon Auto here:
View attachment 2580775

Now, as far as what I know of cocopeat, unwashed / unbuffered coco will have an excess of K and Sodium. But it was washed, and buffered. In this case, the K and Sodium are knocked out of the Cation Exchange Sites, and Mg and Calcium take their spots.

My water does have Calcium and magnesium in it - as per bottler’s specs. But very little potassium.

But as I mentioned, the potassium sulphate was the first bit of “nutrient feeding” the plants got, and that was only after symptoms were becoming alarming. The goal was to have a “just water” grow using a modified coots mix.

This is where I bow out. I'm unable to assist with gardening at an engineering level.

perilousp · Dec 22, 2025

Ninjadogma said:
This is where I bow out. I'm unable to assist with gardening at an engineering level.

Fair enough, thanks for the insights man.

Coots Soil - K Deficiency in flower

Coots Soil - K Deficiency in flower

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