If they're that big and you've gotten to this stage twice before, I dont think its your water.

You said its 80 with the lights on, and 'hot as shit' with em off. Try to keep the day and night temp fluctuation no more than 10-15degrees.
I think its from the heat when the lights off. Do you have it outside er sumthin?
Do you have an exhaust system in the tent?, if so just leave it on to suck out the hot air during that time
SmokeMyPiece Reviewed by SmokeMyPiece on . plants are dying this has happened before all my bigger leaves get discoulerd yellow sometimes even brown and crusty then all the little leaves die and im just left with the bud and it eventually dies as well i cant figure out whats happeneing. maybe its too hot since im having heat problems but ive had a lot of problems the last two crops and need some help. Rating: 5