Here is what seems to be happening to 1/2 my tomato plants.
I plant in multiple areas in the yard and it is happening in most areas.
Everything looked good before the 13" of rain in 13 days.
13" of rain is more than enough to cause all sorts of fungi and bacteria to take over Dean. Heavy mulch would have prevented some of it but it is too late to worry about that now. ;) And with 13" - even mulch won't prevent molds, fungi, and bacteria from developing.
I can't see any of the leaves close-up well enough to be specific so you could be seeing several different processes going on (blight, bacterial spot, nutritional deficiencies, etc.). You can try spraying with a fungicide (Daconil or Ortho) and see if you can't slow it down - it will take repeated sprays - but once it gets established elimination is impossible.
Meanwhile I'd remove all the infected foliage and some of the good leaf branches to eliminate the overcrowding there and improve the air circulation in among the plants. Then hope it will dry out weather-wise. Good luck.
My plants look exactly like this. I posted earlier (Yellow Leaves)and added a pic. I've recently learned that I've been over watering and I suspect this is the cause. I also have some pretty heavy growth and not much air circulation around some plants. Could this be the reason it's taking what seems like an extraordinarily long time for my tomatoes to ripen?