Leaf issues in late flower. Experience needed

lockedshed · Jun 17, 2026

Hi

Its week 12 since 12/12.
3 out of 4 plants are ready to be chopped but I have to chop and dry all of them at the same time.
There is a heat wave coming so I have to wait until a small window,near the end of next week (hopefully) to cut and start drying.
If its 31c outside, I struggle to get the tent 27c lights out (which is day time) with air con on full blast, for many reasons, hence why im waiting until the weather cools to start drying.

Anyway, I have some issues with my leaves and I'm just wondering how I can fix it and get through to drying.
I dont want them to get worse and maybe cause mold when drying.
I have leaf burn on all the plants, but its more noticeable on some.
The first 2 pictures are what im wondering about mainly, but any other issues you can see and help with would be greatly appreciated.
I had nitrogen toxicity as you can see from the clawed leaves but ive been on low ec 1.2 feed and no cal mag for around 2 weeks now, pH 5.80 fed twice daily.

I had built runoff ec up to around 2.3, from an input of 1.7, so I flushed shit loads of ec 1.2 through 2 weeks ago, and have been feeding that ever since.
Runoff ec quickly builds to 1.5/1.6, due to heat i believe, so im feeding like 4 - 6 litres each, twice daily (growing in 5 gallon fabric pots) and getting litres of runoff just to lower ec to 1.4.

4x4 tent
4 photoperiods - humbolt blueberry headband, humbolt green crack 2.0, RQS purple punch x 2.
12 weeks since 12/12 flip
Lights out temps - 24 - 25.5 (hit 27.5 once, maybe more coming up)
Lights on temps - 26 - 29c
Canna coco premium pre buffered coco and perlite 70/30
Canna coco A + B only
Mars hydro fc6500 730w, on about 45 - 55% recently.
One of the purple punch has harmed and is growing seeds, and i think blueberry headband is doing the same but less developed.
Heat stress related issues think.

compostmike · Thursday at 1:25 AM

That looks more like accumulated stress/salt burn plus heat than something you’re going to “fix” at week 12. The clawing/dark leaves say the N was too hot earlier, and the crispy margins/tips look like the coco root zone has been swinging EC as the plants drink harder in the heat. Once that tissue is cooked it won’t recover, so I wouldn’t chase it with more products now.

At this point I’d just keep them limping cleanly to chop. Low EC feed is fine, pH 5.8 is fine, keep good runoff but don’t keep blasting huge flushes unless the runoff goes crazy again. In coco you still want some feed in there, not plain starvation. I’d also back the light down a touch if temps are climbing, keep air moving through the canopy, and pick off any fully dead/crispy leaves that are tucked against buds.

For mold risk, the dead leaf matter sitting inside dense buds is more of a concern than the burned tips themselves. Open a few tops gently and look inside for grey/brown mushy spots or a dead sugar leaf that pulls out too easy. If you see that, cut that section out now. If not, I’d focus on RH/airflow and getting them into the best drying window you can. Those plants are basically asking to finish, not be “corrected” anymore.

lockedshed · Thursday at 5:18 AM

compostmike said:
That looks more like accumulated stress/salt burn plus heat than something you’re going to “fix” at week 12. The clawing/dark leaves say the N was too hot earlier, and the crispy margins/tips look like the coco root zone has been swinging EC as the plants drink harder in the heat. Once that tissue is cooked it won’t recover, so I wouldn’t chase it with more products now.

At this point I’d just keep them limping cleanly to chop. Low EC feed is fine, pH 5.8 is fine, keep good runoff but don’t keep blasting huge flushes unless the runoff goes crazy again. In coco you still want some feed in there, not plain starvation. I’d also back the light down a touch if temps are climbing, keep air moving through the canopy, and pick off any fully dead/crispy leaves that are tucked against buds.

For mold risk, the dead leaf matter sitting inside dense buds is more of a concern than the burned tips themselves. Open a few tops gently and look inside for grey/brown mushy spots or a dead sugar leaf that pulls out too easy. If you see that, cut that section out now. If not, I’d focus on RH/airflow and getting them into the best drying window you can. Those plants are basically asking to finish, not be “corrected” anymore.

Excellent information thanks.

The only issue with watering is that if im not putting lots through, I get more or less instant upping of runoff ec.
So even though ive put gallons through at 1.2 ec, the runoff never gets to 1.2.
It always stays at 1.4 minimum.
If I then water my normal amount (1 6 - 2.5 litre, twice daily depending on which plant)which used to get me about 20% runoff and would be near the input ec for days/weeks, my runoff ec goes up by 0.2 each day now.
Example- 2.5 litre, ec 1.2 in, 20% runoff. Ec out will be 1 4 one day, 1.5/1.6 the next, then 1.8 ...etc. it builds very quickly so I go back to putting more through to lower it.

Also, its hard to gauge how much to water as after I flushed the coco, my old feeding amount will now produce way more runoff than previous, and even with that excess runoff, the ec still climbs.

What is a max safe runoff ec if im putting through 1.2 in, and what should I do when/if I reach that number?
And there is nothing i can do about the margins in pics 1 and 2? Just leave them and do what im doing whilst looking for dead bits near buds/bud rot?

compostmike · Thursday at 6:46 AM

lockedshed said:
Excellent information thanks.

The only issue with watering is that if im not putting lots through, I get more or less instant upping of runoff ec.
So even though ive put gallons through at 1.2 ec, the runoff never gets to 1.2.
It always stays at 1.4 minimum.
If I then water my normal amount (1 6 - 2.5 litre, twice daily depending on which plant)which used to get me about 20% runoff and would be near the input ec for days/weeks, my runoff ec goes up by 0.2 each day now.
Example- 2.5 litre, ec 1.2 in, 20% runoff. Ec out will be 1 4 one day, 1.5/1.6 the next, then 1.8 ...etc. it builds very quickly so I go back to putting more through to lower it.

Also, its hard to gauge how much to water as after I flushed the coco, my old feeding amount will now produce way more runoff than previous, and even with that excess runoff, the ec still climbs.

What is a max safe runoff ec if im putting through 1.2 in, and what should I do when/if I reach that number?
And there is nothing i can do about the margins in pics 1 and 2? Just leave them and do what im doing whilst looking for dead bits near buds/bud rot?

Yeah, that’s the annoying part with coco late in flower. The runoff won’t always match input once the plant is drinking hard and leaving salts behind, especially with heat pushing transpiration. I wouldn’t chase 1.2 out just because 1.2 is going in.

If you’re feeding 1.2 and runoff is 1.4-1.6, I’d call that manageable. If it creeps toward 1.8-2.0 and keeps climbing every feed, then I’d run more of the same light feed through it until the trend comes back down. I still wouldn’t hit it with plain water unless things get really ugly, because coco without some feed in the solution can swing on you.

Those margins in pics 1 and 2 are done though. That leaf tissue won’t repair. Best you can do now is stop it getting worse: keep the EC modest, back the light off a bit in the hot spell, keep air moving, and remove any dead crispy bits that are tucked into the buds. The burnt edges themselves aren’t the mold risk so much as dead leaf material trapped inside dense flowers.

Ninjadogma · Thursday at 1:07 PM

lockedshed said:
Excellent information thanks.

The only issue with watering is that if im not putting lots through, I get more or less instant upping of runoff ec.
So even though ive put gallons through at 1.2 ec, the runoff never gets to 1.2.
It always stays at 1.4 minimum.
If I then water my normal amount (1 6 - 2.5 litre, twice daily depending on which plant)which used to get me about 20% runoff and would be near the input ec for days/weeks, my runoff ec goes up by 0.2 each day now.
Example- 2.5 litre, ec 1.2 in, 20% runoff. Ec out will be 1 4 one day, 1.5/1.6 the next, then 1.8 ...etc. it builds very quickly so I go back to putting more through to lower it.

Also, its hard to gauge how much to water as after I flushed the coco, my old feeding amount will now produce way more runoff than previous, and even with that excess runoff, the ec still climbs.

What is a max safe runoff ec if im putting through 1.2 in, and what should I do when/if I reach that number?
And there is nothing i can do about the margins in pics 1 and 2? Just leave them and do what im doing whilst looking for dead bits near buds/bud rot?

If the pot has been sitting around 2.5 for the past week or so it's actually fine but it's time to start bringing the number down for the plant wind-down. If your output is higher than input then use just water until the output matches your EC goal. Looks like it would be just coming out of peak demand. I'd aim for around 1.8 - 2.0 right now and continue tapering from there. Unless you're running a supercharged setup, ie CO2, the highest you ever want to see that number is around 2.5 and that's during peak flower.

Leaf issues in late flower. Experience needed

Leaf issues in late flower. Experience needed

Yellowing - Late Flower

Grow setup

Intake photos

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compostmike

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compostmike

Ninjadogma

Leaf issues in late flower. Experience needed

Leaf issues in late flower. Experience needed

Yellowing - Late Flower

Grow setup

Intake photos

lockedshed

Attachments

compostmike

lockedshed

compostmike

Ninjadogma

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