Leaves curling in slightly

can anyone tell me why the leaves would curl in it is only slightly they are 2wks old, i raised the lamp using a400 hps so i figured it was to close, also how old before nutrients are to be given, cause i gave the little ones some already, they have been getting it for a week and are growing great, until today i saw the slight curl. have 11 seedlings when can i repot them

Pls if anyone can tell me the answer to this i would greatly appreciate it.

the leaves look like it may be trying to retain as much water as possible... this i don't know why maybe a nute lockout or the ph of the soil. the soil looks watered correctly and it shouldn't have a problem.

what is your ph like and what is your humidity.

I live in a very low humidity climax, so i had to get a humidifier it averages 35-45 I have honestly not checked the ph, this is my very first grow and i am learning on the way. I have ph kit with the pills but have not taken time out to do it. and these two older ones are swagg seeds, my new seedlings are only 1wk old and they are my good seeds, was practin before they came and the girls came up.
As for my girls do you think I had went to long between watering? i had waited 4 days because of size of pot. the pics were took hr after waterin

this happend to my plants when i first started..it was from to much nutes..u shouldn't use nutes. untill the 4th week! if they keep getting worse then just flush them!good luck man!

thanks, i think it might be the nut's, i have not been giving max amounts, however they may be to young. they have not gotten any worse, i hope they don't, i don't know anything about how to flush, i'll probably drown them. but lets hope for the best.