Oozleanswered grow question 2 years ago looks kinda like a mag deficiency, yellowing of edges on lower leaves + sad plants.
maybe root problems too. Both effect leaf turgor.
80f/40% humidity isn't a great VPD for veg, so that will exasperate any problems u have because it forces the plant to drink more.
If you can get the humidity higher, 55-60%+ would be a lot better, or lower ur temps.
So most likely just a PH issue, like thundrfuk said, maybe the VPD or root problerms making it worse.
good luck.