What is causing this damage to my tomatoes?

That is GREAT news, GG!!
I get onew or two of those sick toms every few years and I just remove them and get on with it. The plants just continue bearing fruit and the anomily does not return and the plant does nopt die. I saw no reason that your's would either.
I am very happy that your plants are behaving as they should.

 

Topping off tom plant info has been very helpful. My toms have reached the top of our greenhouse, I think I need to start topping those taller ones off to help the fruit along.