mate is it was nute overload u would notice it on the bottom leaves first , it could be a few things . use this link it should help u find out what the problem is .http://www.ganjagurus.com/overgrowfaq/index.html?
i think it might be ur PH , do u know what the ph of ur water is before u add the nutes and what is it after u add them , also how far is ur light away from the tops of the plants and what type of light is it ( it could be heat stress as well , do u know the temp of ur grow room ) , any way what i would tell u to do is to flush them if u know they are not over watered, use 3 times the amount of water to the size of ur pots or until the water runs clear . i hope this helps.
SH