Wow, that description is exactly what happened to all my tomatoes, for the last three years. I moved the location this year by about 30 feet, and yet the first one wilted about a week ago, and overnight, number two has joined in. This eventually spreads to the other plants. My cucumbers do the exact same thing. No damage, no discoloration, and no solution. I am still trying to find out if there is someplace (I live in MI) that you can send diseased plants that will diagnose the problem for peace of mind and future prevention. Sorry!

Did they wilt right after they were transplanted? Sometimes that happens and it takes a few days for them to perk up.

Most diseases, including viruses, display other symptoms. Most diseases don't kill that quickly.

One thing you might check is to see if the roots were damaged by voles or gophers or some such critter, depending on where you live. That would certainly cause wilt without any other symptoms.

Another thing to consider would be some sort of herbicide, but that usually shows up as deformed, stringy, curled leaves.

Look for your local Cooperative Extension office. For Gardennewbie that would be the MSU Cooperative Extension. In New York they're affiliated with Cornell. I don't know where Nancy lives, but you should be able to google "your-state-name cooperative extension" and find one near you.

Thanks. I think I may have a critter in there. I hadn't thought of that. Thank, I'll start sprinkling cayenne and figure out a way to make it less comfortable in there.
Nancy