HELP! What is going on ....Please Help!! Me figure this out

[DT2000]

the plants are at day 30 of flower everything up top looks great but bottom side doesn’t....my EC is 1.7 and ph going in 5.8 What will cause this issue the tips darken then leaves pale then edges turn brown then they fall off...I’m growing in coco....does anyone have a clue what is going on ..my thoughts was phosphorus deficiency but don’t actually know it is the lower older growth that is affected

[Gingerbeard]

Looks promising.

https://www.growweedeasy.com/nutrient-burn-cannabis

[Mr.furley]

How many are we talking here, 5? 50? Bottom leaf will drop off especially with a bushy canopy as the plant is finishing.

[DT2000]

It’s not yellowing like nitrogen being used up just leaf tips get that burn then they pale then the edges turn brown leaves contorts then they fall off dead

[Colombo]

Are you growing DWC or soil?

[DT2000]

I’m using coco coir

[Colombo]

Do you water often? Coco coir has poor water retention and and if your plant uptake is more than you are watering/feeding your plant tops take from the bottom leaves and branches to matin their health feeding the buds (top of plant) leaving the lower leaves to yellow and die off. By trimming some of the large fan leaves in flower allows more water to the buds and not the big fan leaves. It is part of the life cycle.

[slickdawg]

what’s the runoff Ph?

indoor grow box (coco coir)
40”h 28”w 28”d is my box
have a led grow panel 13" with full spectrum and 225 LEDS got 1 plant she’s in the end of the 9th week! three days into flower. “Krippler” is her name!!
im doing LST training on my plant
i have a passive exhaust system with a fan for air flow

[DT2000]

Runoff on the chem4 og is 5.3 runoff on princess haze is 5.1 and runoff on NL is 5.4 these are pretty big plants and when I was feeding them 1.6 EC the runoff was coming out 1.2 EC so I was told they needed more food and they were already doing the problem they have now....Harley smith from npk university talked to me at length and we came up with under feeding and a phosphorus deficiency but like I said the problem started at older growth but is moving up I’m at day 30 and I need to stop the issue so they can finish with fan leaves

[Mr.furley]

Your runoff is to low. Plant are not able to up take nutrient no matter how much you give them.
FLUSH! Runoff Ph 6.0 to6.3

[DT2000]

Also the bottom leaves aren’t yellowing like a normal nitrogen deficiency at end of flowering like normal they have a large triangular brown tip then the edges turn brown and pale then fall off probably 35 leaves in past 5 days