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