Drooping Fan Leaves

Hello all, somewhat experienced grower here (4 harvests under my belt). I have had a really smooth grow starting with 14 plants under t5's for veg and transferred them to under 2 1000w HPS for the flowering stage. BTW i use fox farms products, currently using the tiger bloom. They stretched nicely and i have some healthy looking plants going, but i walked in to my grow last night and noticed that about half of the plants (no particular pattern) were drooping their fan leaves, not necessarily the biggest or smallest leaves, generally the middle and bottom fan leaves of the plants. I've done quite a bit of research and noticed it could be a variation of issues ranging from over/under watering or ventilation/airflow problems... not too sure what it is, and looking to get any help i can from my fellow cheeba-heads?

was this after a watering or did the soil dry up quicker than usual?

Watch a video of cannabis growing in fast motion. The leaves will droop then spring up. Droop...spring up.

She's fine IMO.

Horribly unclear but demonstrates the drooping effect.

It could be rootbound, room too hot, lights too intense compared to where they were. Drooping still after watering is stress.

This was 2 days after watering, i generally water them every 3 days, so i was surprised to find the soil dry already.... I have switched to watering every two days now. the plants seem to need more water, it was also a hot day of accidentally leaving the vent closed... Thanks for all the replies! I dont know how deep the roots would be but the plants are 4-5 ft tall in 5 gallon buckets, 14 under 2000w.