Is it possible the high heat in the greenhouse did this to the tomatoes? I did not find any bugs on them and it seemed to happen when the temps got in the 90's in there. Doesn't look like sun scorch, but something is going on.
Have you sprayed them w/ anything? Sometimes if you spray insecticide in a hot greenhouse the leaves of your plants can burn a bit. I did that to my tomatoes and as soon as I stopped spraying they were fine. The bottom leaves are still ugly, but they are very healthy.
If not, is this on all your tomatoes or a select few?
When did you plant them?
Is this a variety you have grown before? What variety is it?
If you answer these questions it might make it easier for others to help you diagnose the problem.
I have not sprayed them with anything, I have sprayed other plants in the greenhouse with a soap spray for white flies, but I never had them on the tomatoes. This is on all the "Napa Grape" tomatoes, which very in age but all in the greenhouse. First time with this variety. Some in 4" pots and some now in 5 gallon buckets. The ones in the pictures are the ones in the 5 gallon buckets and they are about 5' tall. They were started in the greenhouse from seed. It's really weird because the plants have been beautiful until now and it seemed to happen overnight. The only thing I can say happened that particular day, was that the temp went up to 96.
I had similar issues with a small tomato plant that I overwintered in the GH. It turned out to be spider mites which my eye could not pick up. The new growth always came out looking good. Not saying that is what yours was but will advise you to watch the new growth just in case.