How close are the leaves to the tubes? If they are touching, or possibly within an inch, they likely will get crispy. Overfertilization is also a possibility.

What specific varieties of plants are showing this problem, and do you have other that are OK under the lights?

I think I have this problem solved.
I moved the lights up about 4 inches and moved the larger plants out into the growing area. I think I kept them in the seeding area way to long. Most have grown new leaves and I have been able to carefully clip off the burnt ones. I also put several of the larger ones in bigger pots. They are doing so much better. At this point I don't think I am going to loose any of them.

As for the fertilization... well I hadn't thought about adding the fertilization till I read your response. I have now made a weekly schedule to fertilize all the plants that are no longer in the seedling stage.
Is this a good idea? If not adding the liquid fertilizer weekly, then how often should I be watering with it?

thank you,
cristi

I'm not a fertilizing expert, but if they're just past the seedling stage, I'd probably do at half of the label recommendations, at least for a while.

Hello,
I fertilize two times a week the plants a foot or taller. The seedlings, clones I like to put into soil which has fertilizer in it already to go. Of course depending on the plant and the needs of that plant.
We use miracle grow around here and it seams to be doing fine. We purchased guano and mixed it into the other plant soil we have for added nutrients. We also throw in coffee grounds, and feed the warms for some of our plants are in the ground (yes inside the indoor greenhouse).
A couple of our plants are going crazy with growth, a arrow head plant, and my sheflara (sp), my umbrella tree, and I think the other is a sage plant, and one of the coleus's. My mother spider plant mr almost killed by taking it out of the bathroom but I fertilize this the same.
The "babies" or seedlings are delicate and to much fertilizer will kill most plants.

One thing I was told a good 30 years ago and hold onto is, the leaves will show what the roots will need. This has held true all these years.

Hope this helps?