Answer: I suspect cucumber wilt which begins with beetles feeding on the leaves and stems. Here's a website from the University of Kentucky (sorry it's not Texas!) describing the symptoms. I chose this site because it has photos of affected plants which you can compare to your own plants.
With your tomato plants, you may be dealing with late blight. If so, planting in a different area of the garden is a good strategy, as is growing disease resistant tomato varieties.
Best wishes with your veggies!
Q&A Library Searching Tips