Light stress and heat stress?

Looks like light and heat stress to me mate. Check your humidity levels if low this can cause this also happen . will just have hot air in there which will cause dropping curling leaves. find a way to lower the temperature and/or increase the circulation in the grow room or grow area if heat is the problem. Having a small fan blowing over the tops of your plants will help prevent hot spots from forming directly under your grow lights. And if you can raise your light may help alot too x 💚 hope your sort it growmie

Without a diary and some pictures that are clear and in normal light, it is hard to say exactly what is going on here, but nitrogen toxicity is one possibility, but without more detailed info about feeding, light height, light schedule, feeding frequency, which strains etc, giving a confident answer is very hard to do.

This isn’t light stress in my opinion. I would flush the medium and eliminate NITROGEN completely and give them PK nutes. It’s highly likely you have NITROGEN toxicity that brought along a PK and cal/mag lockout

be carefull with the water, or temperature on box, maybe is defficit but ease upload other pictures !

above 30c or 86F? (at canopy) if not, less litely heat stress. Light stress will show other issues -- stems will get weak and flop away, pale spots may form on leaves and steadily increase in size until etnire leaves are bleached. Curling down and and cripsiness can be over doing nutrients... as well as underdoing some, lol.. so, it's a fun game that requires you to consider context. Most people over-nute their plants and a number of other non-verified things, myself included on that latter part. If you are soilless, work out ppm from your fertilizer mix.. see if anything is crazy out of whack. eliminate possibilities.. i'd wager low K if lacking and high K/P if not. high k/p can lockout a number of other nutes that'll cause spots then crispiness in the leaves as if it were a Ca and/or Mg deficiency. high S can singe tips of leaves.. but a low K starts with what looks like burn around edges and pregresses. You can see this on my current Nova OG diary. The 'from-seed' plant definitely has a touch of K-deficiency. I know because i feed a very light mix that is very unlikely to lockout other issues and my pH is rock solid consistent with "Jack's" because it is well-buffered. The curling down can be other things, but this too tracks with over-nuting.