1) depth seed planted 2) amount of water as dries out quicker along edges 3) amount of light 4)

A plant has a very strong desire to continue the strain and to do so produces seed that does not all germinate at once. Seed companies work to produce seed that WILL all germinate together as this is what gardeners want. If in nature all of a plants seeds germinated together any problem could cause the loss of the species. If however some seeds were left not yet germinated, they would give the plant another chance. Al

All of those seedlings, whatever their size and appearance look as if they a really struggling. The green algal growth shows that the potting mix is too wet. Next time hold back on the watering a bit and I think you'll find the seedlings do a lot better.

Does this container have drainage?

The container has a large number of small holes, But I do tend to keep it wet. Probably too wet.

Hi Garf,
You are in Zone 10B; I am in zone 8b/9a in Fl. Just wondering why you are not growing these seedlings outside in your zone.
I am growing a lot of seedlings outside now - most in the ground and some in pots. I don't even try to grow them inside because of the bad luck I had. Air can get too dry; container does not have the right moisture; poor light, etc.
I gave up on seeds until I saw all of the volunteers I got in my garden. I thought that if mother nature can grow things from seed in my garden than certainly I can. So I grow seedlings outside, mostly directly sow in the ground. And if I have sensitive seedlings in containers, I bring them in when a freeze is expected.
I use bigger plastic pots; fill them with crumbled up plastics containers (prefer the 6 pacs that small plants come in) then add a layer of Miracle Gro seed starter soil. That way the seedling gets the dirt it needs plus great drainage and light, plus I don't waste a bunch of soil to fill the pot. (This comment really applies to zone 9 and up).
Bob

I don't start anything inside. My main problem was rain drowning the starts. I still tend to keep the starts too wet. It's hard to judge when and how much water to add.

I cut back a little on the water and it seemed to help. I'm still afraid if the babys drying out.

Almost all tomatoes sold today are hybrids (like we humans are all hybrids). So, unless very special precautions are taken, all the seedlings produced by cross-fertilization will be hybrids. Some will have blue eyes, some brown, some will be tall, others not. The only way gardeners can avoid this variation is by cloning. The natural method is a lot more fun....