You don't want your soil to hold too much moisture. Lots of problems are caused or at least exacerbated by overly wet medium.
Looks like your soil (s) are/were too chemically 'hot' for young seedlings. They may grow out of it or not, but they are pretty stressed... You'll want to flush with water at correct pH, make sure the ventilation and temperature in the room are correct, and go a lot easier on watering in the future.
If you have a 'grow' fertilizer with micronutrients, in about a week, make a VERY VERY weak solution about 1/5-1/4 what the label says and LIGHTLY mist the plant with this. I can't tell how many nodes you've got since it's apparent that leaves have alreaday dropped. Heck, you might be ready to do the foliar right away. Count... 5 nodes= ready to start lightly feeding. Those seedlings look locked out and hungry, but contributing to the existing problem in the soil will make it worse.
At next transplant, use MUCH more perlite in your compost mix! Drainage=good!
stinkyattic Reviewed by stinkyattic on . Young Plants are greying! Hey guys, These WW plants are just a couple of weeks old, and I think they got too hot because my girlfriend closed the closet door for hours. I was using a pretty shitty soil, I found out...wasn't holding moisture well at all... I've since transplanted them into Gardener's Gold Organic Potting Mix. The new growth looks good, and I think I just burnt them, but I wanted you guys to take a look and tell me what you think. Pics are not that great, from a camera phone. Rating: 5