Leaf issues in late flower. Experience needed

[lockedshed]

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]

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.