Largest plants' leaves curl down. RIU help me out w/ advice! Pics

Ok so I have 8 NL #5 feminized gals growing in my tent. Under a 1000w set at 24in above the canopy. Canopy temps range from 77-81 lights on. Usually 68-70 lights off but has gotten as low as 60..

They're potted in FFoF 3gal pots. Been 4 weeks since transplant. Last watering before today was 8 days ago. Waited till the soil was mostly dry and watered again today with 1/2 strength grow nutes, full strength FF Big Bloom and half strength Hygrozyme. PH was 6.5 in and out.

Should I be worried at all? Is it overwatering? Hard to believe with waiting 8 days to water...Only the big ones (3/8 )are being affected really.
First pic is the biggest and most affected plant
(Colors look off because of flash/HPS.. All growth is nice and green)

I'm starting to think it's from constantly changing temps... I have an A/C in there and a fan in the other corner that blows the air around and points at the girls...Everytime the AC kicks on they're getting a blast of colder air. Going to move the fan to the other corner.

okay, well I can tell u with most certainty 8 days is too long especially with a 1000 watt. ur better off watering by weight/hefting. Actually mj plants dont like to be dry, they r like u, never want to feel bloated but dont want to feel starving either. Ideally u would keep the medium mostly moist on a continual basis. Only because it is better to water until runoff, is the wait for a few days better, so we can achieve that without overwatering. If they r all green, then other then that u r doing great!

I had to wait that long because last watering was a full on flush... The PH was way high and they had Iron deficiency (from lockout).. Had to wait that long for the soil to dry out some.

Anyways, I rearranged the room a bit so the ACd air isnt going as direct to the canopy...Hopefully this fixes it.

I honestly see nothing wrong, they are fine. just large leaves=sag no biggie holmes