What are we dealing with Here?

It looks like either heat stress were they are starting to curl up on edges, or possibly the inner airflow (from fans) is too high causing faster evaporation, even though humidity is high, if the plant is being pushed constantly by wind/air they will conserve moisture by doing this. I hope any of this info helps as I had a similar problem running hps and trying to keep area cool with fans. Best of luck ✌️💚

agree with Organoman seems like Ca excess and Mg lockout adjust ur Ca ppm

Leaf edges, turn up, classic sign of plant overheating, not taking up enough water to handle the cooling requirements of photosynthesis. 60-70rh ? Are you controlling that overnight when it spikes to 80rh? With no transpiration at night, how is the plant performing gas exchange in rh of 70?. Answer is it's not. Vastly reduced if so. Get your temps cranked to 86 daytime, drop rh to encourage evap at night, 50% no higher. Water cycle is not efficent. Water doesn't wanna leave leaf into air at high humidity and low temps. Just happy to sit in the medium and not move. If you have time. Look up. Cellular Respiration. Root respiration. Transpiration. Evaporation. Evapotranspiration. The Soil-Plant-Atmosphere Continuum (SPAC) refers to the interconnected system where water and energy move from the soil, through plants, and into the atmosphere. It's a complex system of three subsystems that interact to transport these resources, with the soil being the only subsystem significantly influenced by human activity. Understand this and solve 90% of your problems.

Magnesium deficiency can cause leaves to curl up at the edges.

is there a fan pointing in this direction? usually when it is damage around leaf serations it's related to K, but i don't think that's the case here... doesn't quite look right for that. Looks like some fall colors on the leaf that's in background/blurry.. if that's the case maybe it's getting too cold at night? if this is on a 12 hour schedule, you can probably go up near 800-900ppfd (if acurate measurement) and if on 18 hours, stick near 500-600. PPFD without hours of operation (= DLI) is half the picture and half useless without hours of use.