Brown/burnt edges and tips - mid and late flower plants

So I've noticed some browning and burnt crispy tips and edges of the serrated fans leafs. Some leafs are curled up at the tips on the worst plant (furthest in flower).
I let it go for a while and hasn't improved. Nothing has changed as far as nutrients, EC, pH, or lighting. I did add more PK booster (Greenleaf Nutrients - Bud Explosion) on the last two feeds but the issue was already there before I did that. I had initially thought it was a potassium deficiency starting so I had added more for a feed before I rethought the issue.

I can only assume the plant no longer like the current amount or mix of nutrients at this stage in their life. Thinking possibly overfed?

Group of four autos at different stages of flower. One is close to finished and is showing the worst symptoms, the others a weeks behind and show minor symptoms. All the deficiencies are showing towards the top of each cola, so newer growth. I initially had thought it was light stress but the really low leafs on the smaller plants showing deficiencies too would disprove that.

Light: Timber Fatty VS @ ~28" from canopy and not full power. TBH I don't know what it's drawing out of the wall, I need to get one of those outlet meters.
Temp/RH: 77 F/ 40% RH
Medium: Coco coir/perlite
Nutrients: 2 ml/gal CAliMAGic, 3 g/gal MegaCrop, 1 g/gal Bud Explosion, 1 g/gal Epsom Salts = 1.6 EC @ 6.0 pH
Current fed: 2 ml/gal CAliMAGic, 2.75 g/gal MegaCrop, 0.75g/gal Bud Explosion, 0.75 g/gal Epsom Salts = 1.4 EC @ 6.0 pH

They are hand watered twice daily. They each get about a little less than 0.75 gallons at each feed.

Have you checked the ppm and ph of your run off? With those tiny feedings im guessing you aren’t getting any?? The way the issue progresses with age I’m betting you have a build up in your coco causing lockout. I’d expect a high EC and low ph. You are running a little cool ambient temp as well meaning your leaf temp will be even lower. Why do you feel the need to water twice daily?

Dape Green said:

Have you checked the ppm and ph of your run off? With those tiny feedings im guessing you aren’t getting any?? The way the issue progresses with age I’m betting you have a build up in your coco causing lockout. I’d expect a high EC and low ph. You are running a little cool ambient temp as well meaning your leaf temp will be even lower. Why do you feel the need to water twice daily?

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Each plant getting 1.5 gallons of feed a day is tiny feedings? Yes I'm getting plenty of run off each feeding. Why feed twice daily? Because it's coco.

Hey man, I’m not the one running to strangers cuz my grow is shit. Drop the attitude and accept criticism.

Your problem is in your root zone. And watering like that “because it’s coco” tells a lot.

Dape Green said:

Hey man, I’m not the one running to strangers cuz my grow is shit. Drop the attitude and accept criticism.

Your problem is in your root zone. And watering like that “because it’s coco” tells a lot.

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Sorry should I have explained the benefits of multi feeding coco instead of just saying "because it's coco" because you don't know any better? You got it. My grow is shit. Thanks for finding the problem. What exactly is the issue in the root zone, since you have it figured out.

Lol, looking at my coco grow and it sure doesn’t look like that man. My buds are bigger and don’t even have a brown hair yet. Yes, you can overwater coco.

Dape Green said:

Lol, looking at my coco grow and it sure doesn’t look like that man. My buds are bigger and don’t even have a brown hair yet. Yes, you can overwater coco.

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Go away troll.

Don’t think you can overwater coco?

Dape Green said:

Don’t think you can overwater coco?

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In a fully root bound pot. No.