looks like grey/black leaf spot...alternaria spot. also, your soil might be magnesium deficient (maybe due to pH or level deficiency) given the look of the older leaves.

The problem in the other post is leafminers. The problem here is different. The whitish areas on the leaf to the left appear to be collapsed tissue. Could have occurred due to a water shortage -- possibly hot weather? very low humidity? If that's true, the small black lesions could be a secondary infection, especially if the plants are now in a more humid environment.

I have never had a problem with tomatoes until I notices a couple plants had a large amount of yellow leaves with black spots on them. The plants were growing so well until now. It has only happened in 3 of the 10 plants so far? I have removed all the branches so far that look sick. What is it? what can I do? Rob Pittsburgh, PA

Thanks for all your responses! I looked closely again at the leaves and I believe I have thrips. UGH!! There are some tiny yellow/orange super slow crawling things on the leaves. So mad! I have no idea where they came from, especially since I live in a high rise in the city and my window is only occasionally open to air out my plant. I made some homemade chili pepper (serano) and garlic spray and sprayed the plant...I hope that solves it? Man...growing a plant is a lot more difficult than I though it would be. ;p Fingers crossed the spray kills the thrips and not my plant.