Strange leaves please help !!!

Hello Can anyone tell me why this uper leaves curling into themshelves from the sides ?
Thanks for any help!!!
5 weeks veg indoor growing.
Start from seedling feminized and transplant after 2 weeks.
4 white widow every one in 24 L container with soil all mix.
Temp 28.5 C humidity 75-80% but after this before 2 days lowered the
temp 26 C and humidity 55-60%.
Light fluorescent 5500k 5500 loumen and 6500k 3000 loumen = 8500 loumen 45 cm from the top.
Nutrients HESI 1/2 (ROOT COMPLEX AND SUPER VIT)from directions but whitout the TNT.
Added before 5 days iron (fe) 10ml in 10 L of water.
PH 6,5
KH i dont now.
 

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