White Widow showing signs of trouble

this is day 24 under a 400w mh conversion bulb. i haven't added any nutes yet, just water. what could it be?

It's time for nutes. I'd guess nitrogen def.

yup, same symp's as nitro. def.
iv had the same problem with mine but it went really bad n killed everything. i was nutin n all.
hopefully urs wont do like mine,
have u folier fed them wit anythin? n wt nutes do u use?

plants telling you she needs some food, give her 1/4 strength grow ferts, when the plant gets light like that thats the sign to feed, when she gets dark green almost blueish its too much