the photo isn't too good, but it looks as though the leaves are showing signs of nutrient burn ... you should NEVER fertilize seedlings in the first 3 weeks ... flush them good with plain water a couple of times ... don't worry, they will recover OK ... plants will show sex several days to a couple weeks, after being put into a 12-hour light cycle ... don't put them into a 12-hour cycle until they have grwon thru at least 5 sets of branches, or, better yet, after you see the branches start to 'alternate' ... :smokin: