Definitely over crowded! Should have it's own container that size or larger. Also possibly overwatered, which will cause yellowing. Full sun is a good thing. Not to late to repot, it might recover

All of those things would prefer their own pot because of the different needs they have. The tomato looks like it might recover and grow if given it's very own, larger (perhaps much larger depending on variety) container. Soon. It also looks like maybe it has had too much water recently. Cheers!

Cindy,
I think tomato plants are a lot easier to grow in the ground. If you can find some room in the garden it could make your first tomato growing experience more enjoyable.
Gail