What is wrong with our tomato plants?
My tomato plants have turned yellow and brown and the tomatoes themselves, before fully ripened, died on the vine. Is there a reason for this? The bed is new this year, but I've followed the same process I've used in previous years (with no issue_ by creating it lasagna style with newspaper, compost, and mulch to create the bed. Once the bed was ready to be planted, the plants were mulched. The plants are from our own seeds, not from a grower or retail outlet. We tested two different groups of plants - one receiving water regularly and the other group watered minimally after July 11. Both sets look similar, with the more-watered group looking only slightly more worse for wear.
Your tomatoes probably have late blight. The disease pressure has been strong this year. Unfortunately, there is not much that can be done at this point. Protectant fungicides are effective, along with clean sanitation in the garden and other practices as found at the links below.