I have a couple of comments.

I think you are starting them in too big pots. A seedling doesn't need that much room and it is harder to keep the right moisture. I have never liked peat pots and won't under any circumstances use them. They suck the moisture from the soil and they can grow mold on the pots. Do not plant them out in the pot. I know they say they are biodegradable and the roots grow through them but they don't tend to. Years ago when I did try them I dig up a tomato that was in one and the root ball was still in the pot and had not gone through it.

I use disposable drinking glasses--not the clear ones. Styrofoam ones are small for smaller plants. 16Oz. plastic ones are for larger plants like tomatoes. I buy my Styrofoam ones at the dollar store--25 for $1--the plastic ones at Walmart--50 for $3. You can throw them away or do like I do and wash them in a bleach solution for the next year. I start my seeds in a shallow communal pot. I like the plastic mushroom containers they measure 5"x4" by 2" high. Then I transplant them into the glasses when they are getting their 3rd set of leaves. I sink the Tomatoes into the soil up to their leaves and they grow roots all along the stem(only Tomatoes).

A good way to test if a plant needs water is to stick your finger into the soil. If it feels wet an inch or so down it doesn't need water. Also a pot will feel light when dry and heavier when wet.

Your light set up seems to be fine. but your plants seem to be leggy and that is caused by lack of light. It is likely because they didn't get enough light at the start.

I hope this helps. Gardening is great fun but it is also a learning experience. I have been at it for many years and every year I learn something new.

In addition to everything Dave said, it is unrealistic to expect a huge change in growth in less than a week from adding fertilizer even in adult plants. For seedlings, two cotyledons are supplying everything the plant needs through the growth of the second (I believe) set of leaves. In fact, if the soil you are starting them in has fertilizer already, you risk burning the small roots. Anyway, I think underwatering is better than overwatering, though when they are small both can be lethal. No one who underwaters ever got damping off or fungus gnats, though. :)

Thanks for the information. I've started moving everything out of the peat pots, out of concern over some mildew that's been popping up.