So this might not be the best forum to post this on but so far this year I'm having issues with my tomatoes. I started them in bags end of February. Potted them into solo cups using a different brand of seed starting mix. Most of them were up a few days after I planted them. I have a small set up in an upstairs furnace room that says 60-70 degrees. I have two lights that are 2 bulb T8 fixtures and have 6500k bulbs in them. One of those I just got this year the other I have had for a few seasons. I also have a plant starting lights that I have no info on. My problem is that I don't have many true leaves yet. Only a few plants are even starting to get them. Then the cotyledons are really loosing color and starting curl. I have had the lights 2-3" above them and kept the lights on for around 16-18 hours at a time with about 8 in between. I thought maybe the starting Mix was the issue so tonight I repotted a few. The root systems seem very healthy. One plants roots were almost a foot and a half long with very poor top growth. Right now rotated which plants were under the new lights thinking maybe the new lights are the issue. I might flip a bulb from each light fixture as well. I also noticed that the bottom third was quite soggy so I'm going to cut back on water. The furnace room is un finished and has some drywall dust in it but it isn't in contact or being distributed really but I guess could be the issue too. Am I missing anything or any advice as to what to do to correct this?
More pics
Roots from a repotted plant. Over a foot long
The top growth to the root picture above
First suspect would be the potting compost. Then I'd test a few with a very dilute source of N + chelated minerals.