Today is the first time I fertilized with Miracle Grow (thinking that would maybe help).

so you can rule that out.. seedlings won't need any fertilizer until they have several developed true leaves.
if the temperature is 55-60F and above, that leaves two possible causes, not enough light, or too much water.

They sure don't look like they were very close to the grow lights. They are very long and leggy, which is what they do when they're reaching for light that isn't there. If they don't get enough light, they'll also turn yellow. Looks pretty clear to me. What are your grow lights? Bulb type, wattage? How close were they?

Sun Blaster T5 Type 24 Watt lamp. I also bought Sun Blaster potting base with a plastic dome about 5" high. There is a groove at the top of the dome that the lamp fits in.

the fluorescents need to be 5-6 inches above the seedlings and no dome after seedlings have fully emerged from the soil.

They were green and shorter until the beginning of this week. Then they suddenly got tall and the leaves turned yellowish. I thought that maybe they were getting too close to the lights. So today I took them out of the lights and set them in the sun. And watered them with Miracle Grow. The dome on top has keep them very moist so they could have too much water. This is my first attempt to grow tomatoes from seeds. I also started some violas that look real good, but they are still so small.

I see a few square feet of seedling area in your picture, and I think 24 watts simply isn't bright enough. (Was that 24 watts total, or 24 watts per lamp?) Most of us use T12 (48") fixtures for almost the same area and those put out 80 watts total in two bulbs. Also, many of us in this forum swear by putting the foliage within one or two inches of the bulbs. That is, as they grow, you move the pots down. Seriously. The farther away they are, the less light they get. Fluorescent lights are cool enough that there is no danger putting them that close. It works.

So I'm guessing that if you have 24 watts total, and especially if the seedlings are a ways away from the lamps, those plants are starving for light.

Of course, if you can put them out in the sun, and it's warm enough for them out there, you can just dispense with the lights entirely. In any case, do be careful about overwatering. At this stage, the top of the soil should be allowed to dry out. The roots are way down deep, and that's where the moisture needs to be. Keeping the soil damp on top can produce serious fungal damage, which is called (perhaps not surprisingly) "damping off".

As already mentioned the dome is used for germination only. Once they break the soil surface it needs to be removed.

Otherwise it is over-watering causing the anemic plant color and not nearly, nearly enough light. You are also going to have some chronic problems using those peat pots and one of the most common is they wick water and encourage excessive watering. Try to get the plants out of them ASAP and when transplanting bury all that bare stem deeply.

Have you checked out all the how-to FAQs and the discussions over on the Growing from Seed forum here? They cover all the basics including lighting. And the distance from the lights all depends on the type and size of the lights used. The standard recommendation is no more than 1-2" above the plants when using T-12 or T-8 bulbs 3" with T-5s.

The Sun Blaster T5 Type 24 Watt lamps come in a couple of different sizes of 2' to 6' but their dome set-up is bad for plants. So whichever one you have you need to hang or rig it so that it is NOT using the dome.

Dave

Growing from Seed forum

Just to build on what Dave said, those plants are salvagable, as long as you repot them (or plant them out) promptly, and bury most of the length of those long stems, leaving just the leaves above the soil. Those stems underground will form roots, and as long as you fix the illumination, you'll end up with perfectly normal looking healthy plants. In that respect tomatoes are very forgiving of allowing them to get leggy.

Those do not look like one month old seedlings! Could they be cold? I notice the stems are purple. I sometimes get purple when my plants are cold. I usually have a few sets of true leaves at a month. Like this;

You can salvage them, but if you start over, and have good conditions, maybe some bottom heat, you can probably be right back where you are in a week or so. BTW, I let my lights almost TOUCH the leaves.

Fans to move air would help too.

But, my theory is that your biggest problem is the pulp pots. They don't allow for proper drainage and soil aeration. Your plants are very salvagable at this point but get them out of those pulp cells or at the very least take a utility knife and rip slits down sides every 1/2" apart.

The purple stems are curious and I too have seen them. You'd think it would be telling you something about conditions and nutrients, but the only helpful thing I can find about it is that people growing different varieties under the same conditions find that some have purple stems and some don't. It may be as simple as that.

I've read the purple reflects not getting nutrients where they belong, with one cause being cool temps, but that overall it's not a big deal.

Certainly low phosphorous can cause purple leaves, but I'm not sure what would be specific about purple stems if not variety. I've seen plenty of tomato seedlings grown at cool temps that don't have purple stems.

I'm going with purple stems is due to variety!

Purple stems and leaves are actually pretty common in young immature seedlings. Frequent discussion on the Growing Tomatoes forum. No threat posed to the plant and goes away on its own as the plants mature.

Dave