"Late blight" possibly.
This is not a criticism , but they seem crowded, we all work with the space we have. Also, have you planted tomatoes in that spot before? That can cause issues too.
Don't over water, let them dry out a bit, remove the dying plants asap, use a copper fungicide, and next year replace a lot of the soil if you have to plant in the same spot. If you can, rotate your crops every year.