Well a pic is worth more than words when a problem needs to be diagnosed...other than guessing...are your CFLs close, like about 2 inches away?...are you feeding any nutes? are you giving them cal-mag or even epsom salts?...are you letting water/feed runoff (drain out the bottom)?...if your leaves are healthy green and the tips start yellowing, it means you fed too much...if the leaves are unhealthy and the tips are yellow and curling down it means they're hungry and need nutes and some cal-mag (or epsom salts)...good luck man, and welcome to RIU...