too much ppfd?

Leafs curl like that when charged in nutrients and grow fast. Change nothing. ^^ Get "PPFD Meter" for your computerphone, some measurements for your lamp made by someone serious, and follow the instructions for adjusting the offset in the application. With it, you can learn to adjust the lighting yourself for each harvest cycle (bear in mind that it's not a very precise tool without a real external sensor).

They are green, don't look bleached, are still holding themselves up, and don't look to be sitting short. Either they just started to react to too high of light intensity (turn down power level), or it's too much heat (raise lights or cool better) or the pH is off (correct pH). I don't ever mess with pH on my end, but I have seen similar twisting from just heat and from way too strong light intensity (680w LED in a 4x4). Uni-T A quick infrared laser thermometer reading of the tallest leaf will give let you know if it's heat or not though. To measure PPFD, buy The UNI-T Light Meter UT383BT () and use "PPFD METER" app in app store. Connect to Bluetooth.Choose closest light setting to your lights. Calibrate. Ready to measure. It works nice and I check and use it daily basically. Totally worth the money and the most used tool I own for growing.