Need help. This is my very first grow! Got 6 clones in a 1.5 foot by 2.5 foot closet. 3 on bottom, 3 on a shelf, both have a 600w LED about 24 inches over (maybe less now since theyve grown!).

Look at bottom leaf on far right plant (top). Rest of plant looks fine, but there is a weird looking burn on that one leaf. Also see middle plant (below). There is one set of leaves (again the bottom one) but this time it is much darker and droopy and turns downward:


Most look great, i hope, but there are a few problem spots. Only the bottom leaf has some yellowing here, and turned down claw. rest of plant looks good, but again that bottom leaf:


My friend that also grows said he thinks I messed up my first batch of plant food when I noticed this at first about a week ago. He suggested to give them plain water and let them eat up whats in the soil for several days. I did that, and all new leaves look good, but those old ones aren't going away. Been a couple days since I redid the food and no new yellowing. Do you think I solved the problem or am I overlooking something else? And will the problem leaves get better, or not, and how long will it take? It kind of looks like they may have gotten better, but I cant tell by much in a week.