Any chance of pictures? Very hard to make sensible suggestions without.

Have you fed the seedlings? If not, it sounds like a phosphorus and nitrogen defficency.

I tried to post some photos but I guess they didn't load properly.

I dont know if they uploaded the first time so here they are again. @floral_uk

Yes I did give them the alaska fish emulsion at 1/4 strength a couple of days ago. @wayne_5

While in the midst of trying to take pictures and hold the plant up, one of the stems broke off.

suspect they need water, then fertilizer.

I'd like to know what kind of lighting you're using and the type of potting medium.

While the pics don't look like the "damping-off" disease I have seen check these symptoms to see if they fit your situ...

"Symptoms of Damping-off:

Seeds may be infected as soon as moisture penetrates the seed coat or a bit
later as the radicle begins to extend, all of which rot immediately under
the soil surface (pre-emergence damping-off). This condition results in a
poor, uneven stand of seedlings, often confused with low seed viability.
Cotyledons may break the soil surface only to whither and die or healthy
looking seedlings may suddenly fall over (post-emergence damping-off).
Infection results in lesions at or below the soil line. The seedling
will discolor or wilt suddenly, or simply collapse and die. Weak seedlings
are especially susceptible to attack by one or more fungi when growing conditions
are only slightly unfavorable. Damping-off is easily confused with plant
injury caused by insect feeding, excessive fertilization, high levels of
soluble salts, excessive heat or cold, excessive or insufficient soil moisture,
or chemical toxicity in air or soil.

Above ground symptoms of root rot include stunting, low vigor, or wilting
on a warm day. Foliage of such plants may yellow and fall prematurely starting
with the oldest leaves. The roots of a diseased plant will have some
shade of brown or black and evidence of water-soaking. Healthy roots
are fibrous appearing and are usually white or tan in color. These symptoms
are easily confused with severe mite, aphid, scale infestations, or root-feeding
by nematodes or insect larvae. Environmental factors such as accumulated
salts in the soil, insufficient light or nitrogen, potbound roots, cold drafts,
etc. can be eliminated only by examination of the roots."

I have learned to spray seedlings with a bit of hydrogen peroxide mixed in the water to help prevent damping-off. Just moisten the top layer of soil while seedlings are young - later begin to water from the bottom. Apparently it is the moisture on top of the soil which contributes to damping-off.

Once the damping-off appears I don't think there is anything that can save the plant.
HTH

I have 2 5000k 1600lumen cfl light bulbs and im using a homemade potting mix. I was watering them with rain water and there were these little green things in it but I didnt think (hoped) it wouldn't harm them. I think this could be a factor.

EDA: Forget to mention that I also gave then 1/4 strength of alaska fish emulsion

Not hopeless yet. Try the feeding as suggested and water by placing in a sheet pan, bottom watering. Poke a few hole at the bottom 'sides'. (just up from the sides)...helps water get into those cups. A pencil or nail makes it easy. They also look stuffy. They need air movement like a low running fan.

You can also add some more soil, especially your tomatoes. Just pinch off any lower leaves.

They don't look that bad.

They could use some outdoor sunshine though.

I also like to use rainwater in a spray bottle to wet the soil surface - I just mix in some hydrogen peroxide from the medicine cabinet. :)

what's in your homemade potting mix?