Two weeks ago I planted 72 tomato seeds. I had bought one of those trays that you fill with water, let the cubes raise, then drain off excess water and plant the seeds.

Took about a week and they started sprouting pretty well. Some varieties before others. But it went down hill quickly. I have a bunch of seedlings that look like thread with little bitty leaves on the end. On average they are all about 3-5 inches long.

I kept the whole deal covered to have very little if any light. They stayed moist, not really wet.

First time doing this and I screwed up big time it appears. Would like to try again if I can get some pointers.

"I kept the whole deal covered to have very little if any light"
I'm not a farmer, but after seeds sprout, I think plants need light in order to grow.

The sprouts need light to live. You should not have blocked sprouted seeds from the light.

Keith

As soon as they're up you want light as bright as possible. No standard indoor lighting can hope to match natural sunlight so you need supplemental lighting as strong as possible. I use a four bulb flourescent fixture with full spectrum and daylight bulbs on a adjustable chain drop so the light is almost in contact with the plants. The light needs to be on a minimum of 14 hours a day and won't hurt to go 24 the first week. I also put a small 6" fan on them to exercise and stiffen the stems. Airflow also fends off damp.

If using soiless mix light feed at first true leaf.

That is a fungal issue known as "damping off". The whole tray is likely a write off. Do same as before with the jiffy pellets, but sprinkle a liberal amount of cinnamon over all the pellets before seeding.
Remove lid and provide light as soon as the plants sprout

What’s with the cinnamon?

Ok, I really did mess up then. I was waiting, or trying to wait, until the majority of the seeds came up to get the lights on them. Some of them were up several days before the others. There are still a few just popping up now and even some that haven't came up at all. Can I put the light on them now? Can't see it hurting anything now.

Also, when they sprout you want to keep them almost touching the bulbs as they grow. Use a 5000-6500k flourescent light. If you don't they will get leggy. A fan helps as well. When it comes time to transplant you can bury them in the ground quite a ways. They will put on more root that way and will be less likely to get wind damaged.

Yes, put the light on them now. The ones that just sprouted will recover. When you replant them, pull of the lower leaves and plant them deep, leaving a few leaves at the top exposed.

Keith

Bigbrownie, cinnamon is a powerful anti fungal.
No joke, it increased my success rate by 200% after I started using it