leaves curling help

ok im a first timer. the leaves on my plants are curling they are only 4weeks old. i have noticed that it curls more about 2hrs before the light is put off but i looks worse in the morning n slowly looks better till night rolls round.
the leaves arnt browning though just curling my setup is this:
250watt light 2ft above plants
day temp 25-27...night temp 22-25degC
grow space is 120cmX120cmX200cm
they are in a premixed soil with good drainage
soil ph is 6.6 n water is same
light cycle is 18/6
i only gave them a starter fertilizer that boosts there disease resistance n that was when they first popped out the soil. i thought at first that it was heat so i put a fan in and raise the light but it still the same if not slowly getting worse

any help would be great thanks cos im getting sooooo stressed out

Your day time temps are to hot amigo.

Light might be too close as well

ya your temp is too hot

also the leaves have just started to flip over completly exposing the underside o his leave
i thought 27 was ok all the things ive read say not to go over 30 what should it be?
the light is about 24-27inches away at least n it cant go much higher

Can you make the room a little more humid? Leaves do that when they are trying not to lose water to evaporation/ transpiration.