hard to say by that photo. what week are u in? Its usually 2 things when their this little. Ur PH is off, or overwatering. sorry, 3 things or they aren't getting enough nutrients or vise/versa. what soil did u start with? since u see ur plant better than me start with that list of things if u think its something else go to the plant problems thread here on RIU and u'll probaly be able to match up ur problem better. Its just hard to tell from a photo. If ur hittin week 3 start small doses of nutrients, unless u have some hot soil like foxfarm ocean. that stuff is real hot. go over those things then give me a shout. but it usually something simple like PH, water... dont worry too much yet. just adjust to the problem.. research plant problems and u'lll get it. peace