Why are leaf tips curling down?

Do u have some times in your tent where the heat rises over 30 Celsius? I agree could be slightly too much nitrogen. Its not at toxicity level yet tho. I only comment bc i had this issue in my tent. I really over did the nitrogen tho. My leaves went shiny and dark green and purply. I also had the curled fan leaves but i think that was from too much heat for too long as i was figuring out my heating cooling system and how to control it. But u know what? I still got great bud and a decent amount of it too for a first grow. Hope this info helps. Good luck the rest of the way. i think your plants look great and even if they didnt, its incredible how they recover after the abuse we put them through

Looks like maybe overwater/excess nitrogen, or may be both. Your room temps/humidity look solid, so not sure what else it would be.