Help with my little plants!!

[jmhammRN]

So, for the first time I have started tomatoes from seed. This past Sunday was the 4 week mark since planting. 11 different varieties, including Sweet Ozark Orange which I got from Ozark here on this site, were planted. Things were going really well until tonight when I went to check on them I noticed some problems. The first leaf that caught my eye just appeared as if it had gotten too close to the grow light and got scalded. However, upon further examination I found other problems as well. Now I will do research and probably figure out the problems and hopeful remedies within a couple days but I want to get an answer as quickly as possible in hopes of halting a disaster. And I hope this post will help with some answers.

Here are the pictures:

The first couple are just a view of my little crop under the grow light, 51 plants.

The next two show yellowing on some leaves.

The 5th picture shows some "moss" growing on the soil, only 3 have this -- with this one by far the worst.

Then, the rest of the pictures are my big concerns - Is this blight?? Obviously I have already removed the problem leaves to at least slow the problem. And no the leaves that are cut off and just laying in the soil are not affected, they are just the cotyledons that I trimmed off a few days ago.
--I will admit that sometimes while watering the leaves would get splashed, but I tried to let the top of the soil dry out before watering again.