Hey, I just saw this now.
The miracle grow AND lawn fert combination is just way too much! Back off on that, and give a weak solution of just the MG for now. Weak like 1/2 or even 1/4 of what the package says. That stuff really isn't ideal for cannabis but at least in soil you will find it easier to use.
80' and 40% RH is not a bad temperature. You should not see any signs of heat stress with that- check the temps at the level of the plants too. The curl could be residual from the fertilizer burns.
Just watch to see if new growth starts to improve i nthe next couple of days.
What strain is that by the way? I am very impressed by its resilience!
And I'm a chick...