What is wrong with my tomatoes? I can't tell if it is BLIGHT or WILT. What is the difference?

The symptoms you describe are similar to my experience with bacterial wilt. This usually occurs when night temperatures are warm and your soil is very wet. Clay soil does not release appropriate nutrients when it dries, so moisture must be uniformly retained, but not saturated. I beat that problem by planting Celebrity tomatoes. They do not succumb to bacterial wilt as readily as some other types. Try different varieties until you can isolate what does best with your conditions. Good luck.