Leaves can droop and turn yellow for many, many reasons, although the most common reasons are both underwatering and overwatering.

If the rain (or constant watering) is keeping the soil saturated, roots cannot take up nutrients and you'll have leaf wilt and yellowing.

If there is no rain, though, or if it is hot and dry in general and only a little rain is falling, you get the same symptons.

When leaves are yellowing, that yellowing in and of itself indicates stress. So does wilting. So, you have to figure out what is stressing your plants.

I don't know which part of the state you live in, but many parts of the state have had excessive rainfall.

The fact that you are seeing similar yellowing of leaves in other veggies makes me think it probably is not a problem that is unique only to tomatoes.

If you are having only average rainfall or below average rainfall, then something might be going on in your soil. Is it good sandy loam? Exceptionally sandy? Horrid red clay?

Look at your yellowing leaves. Is the yellowing starting at the bottom and working its' way up the plant? Do whole leaves turn a bright yellow or do only leaf edges turn yellow or do you have splotchy yellow and green leaves? Are there small brown spots on the yellowing leaves? Large, brown concentric circles on the yellowing leaves?

Yellowing leaves can indicate many things. I've linked a previous post where I went into a lot of detail.

Read it and look at your plants and attempt to self-diagnose. Then, come back and tell us what you think and we all can throw in our two cents worth.

And, by chance, to you know if Tomato Yellow Leaf Curl Virus is a problem in your county? It is a big problem in some counties, and rare in others, and I seriously doubt it is your problem, but it is a possibility.

Good luck,

Dawn

Here is a link that might be useful: Yellowing Tomato Leaves