One plant is starting to turn much lighter than th...

when did you water last? My plant will droop like this when she's thirsty but the yellowing is nutrient deficiency. Are you feeding right? Your PH is very high and your probably locking out the magnesium uptake. Nitrogen deficiency starts and the bottom and moves up but Magnesium starts in new growth like yours. She should be starting flower since it's an auto and you should already be introducing flower nutrients. Get your PH lower. You may want to flush, your medium PH is probably to high since you've been feeding with such a high PH for some time

I didn’t see a nutrient schedule on your journal. What are you feeding the plants? The droop I feel like could be some over watering.

Yellow plant just needs more nutrients, slight signs of over-watering or lack of humidity. Nothing to do with too much air