What is wrong with this tomato seedling?

Only my second year doing tomatoes and I failed miserably last year. This year is already quite different with about 20 nice healthy plants. And then I have this one in the picture. It is showing definite signs of disease, but I am unfamiliar with plant disease so I am hoping to get some help from all the experience around here.

The healthier looking leaves on this plant have some darker spots that look like it might be mold starting to get a grip. The damaged leaves have a faded color almost like a chemical burn. I have not sprayed anything on them except a diluted solution of miracle grow a couple of weeks ago. When they were smaller I only bottom watered and now I don't get the leaves wet when I water from the top. Like I said, all the other plants are fine and very healthy, so I am puzzled. I have this one in seclusion until I find out what's wrong.

Thanks for any help.

I think you might have burned the leaves with the fertilizer to cause the lighter spots--I don't know how much you diluted your Miracle Gro, but I don't think it's really intended as a foliar spray so there's a decent chance it was still way too concentrated to spray on the leaves. And I think seedlings would probably be more sensitive to something like that than full grown plants would so it would have to be even more dilute. I can't see the dark spots well enough to know what they are but unless they're spreading or getting bigger it doesn't look like anything to worry about.

Thanks for the quick response. I sprayed the same solution on all the plants. In fact, I sprayed almost every plant that I am growing. From what I have read(and on the package) MG is a good foliar spray I have used the same spray for about a year now with all of my vegis and have never burned any of them. Could it be that this plant happens to be more sensitive? Is that possible?

The spots are very hard to see, even in person. And I didn't notice them until I saw the picture. So I hope you are correct and I don't have to worry about them.

Seedling sometimes do loose their lower leaves for one reason or another. I would remove it. If no other leaves shows signs of the same thing, I would not worry about it. Miracle-Gro is intended as a spray also. You are right about that. However, on seedlings I would dilute it by a 1/4th. It is a good idea to keep it isolated from the rest of your plants.

OK. So both of you agree it is most likely a chemical burn caused by the MG. So I'll take your advice and not worry about it. I will keep it secluded and cut off the lower leaves as suggested by blomma. I will also dilute by 1/4 instead of 1/2 in the future.

Thank you both very much.