I see some of this too on the south end of my bed. That is, the plants that get the most sun. I have to assume that whatever stems die will be replaced. The plant will grow as hard as it can. If it isn't growing on one end, it'll find another end to grow on. My plants are six feet tall, and those topmost tips are hard to pump enough water up to. I suspect suckers lower down will take over for them.

Curiously, I too see no sign of this effect on my seven-foot cherries.

We too had a very cold April, maybe a week of good temperatures, and then hot. I tried to grow heat setting tomatoes, and they still seem to be setting fruit.

My Chilacayote squash in 2015 did what you're describing with tomatoes (wilted during the day when it was sunny and hot and perked up at night). That year, I started them indoors (and grew them extra large, indoors) and transplanted when it was still cool in the spring. When I grew them from direct-seeding in 2017 they didn't wilt in the sun, though (it was already hot when they sprouted, though). My hypothesis is that the sun intolerance has to do with the pre-transplant leaves and/or pre-hot-weather leaves (which are probably adapted to be more sensitive to the sun than the others), and that removing those older ones and letting new ones grow might solve the problem.

I've never had tomatoes do that with the sun, though. It must be pretty strong there in Texas. :)

The thing that is odd is that only the new growth gets wilted. That may be because the older growth is shaded by other leaves, and that the new growth is more tender.

The new growth is on the end of the long stems. It's harder to pump water up to the end of the stems. But the new growth is also most fragile, the foliage is not as thick, and evaporative water losses are more serious. But that's true, it's the new growth on top that tends to be in full sun.