Leaves dying from bottom up

Hey guys,
I'm doing a FMS C99 hempy bucket micro cab grow with a 180w LED. The temps have been a little hot, low to mid 80s at ground level and low to mid 90s a few inches below the light (probably a lot of radiant heat). I'm using Dyna-gro and this plant is a super light feeder: on my first grow 35% of the recommended amount was the most I could feed, and even then I was seeing some tip burning.

About 10 days ago more and more random leaf tips started doing a 90-degree downward claw tip and the plant was dark green. I looked into it and saw that this might be due to nitrogen toxicity, especially exacerbated by the heat. I backed the feeding down from 15% to 10% and have started to see the leaves turn light green and go bye bye from the bottom up. The pH has been solid 5.7 - 5.9. All I can think is that the plant is starving and I should up the feed and run the AC all the time to keep temps down. Can anyone help me out?

that black on the leaves looks like phos defiency , also looks a bit like rust , hope its not rust it will not get better ,ever .try some bloom ferts for a couple of weeks . if using tap water check ph 12 - 24 hrs after you have ph'ed it to make sure its not creeping back up tap water will do that especally if its hard water .

I just realized the fucking nutes are over three years old! Agggghhhh!!

Its droopy, how often are you flooding ? reduce flooding by time and frequency. and get some decent veg nutes that work.