3 weeks in to vegetave and have thin leaves slightly curling??help

hi guys
im 3 weeks into my first grow ever,my babies are about 4 inches high aand have 2 sets of leaves .the growth is slow..i think...the leaves are light green,not dark..like alot of pics i have seen.my temps are max 23 degrees and min 7.5 degrees!im usin botteled water and organic nutes 1/4 strenght.ive only used the nutes on one of my 3 girls and she looks slightly darker green.my humididity is between 35 -55 pc.the bottom fan leaves on the plants are thin and curling slightly,sory no pics!is this abnormal...could it be from my fan...do i have to wory...any help or advice would be great...tanx!
 
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