It could be Anthracnose fungus and the most common fruit rot on tomato plants. It attacks mature fruit past the mature green stage and can be treated the same way septoria leaf spot and early blight are treated.

Thanks! I spray with Daconcil, then wait 2 weeks and spray immunox then wait 2 weeks and repeat. I tossed that fruit and will watch it closely.

It seems like many fruits are getting this on that plant - but not as bad. Should I pull the plant?

Note that I am not getting sunken spots but the odd coloring inside is visible and fruit are much softer than normal. When I pick fruits I think are bad it is immediately obvious when I pick it how soft it compared to past years, earlier this year and my other pants far away with no issues.

Other tom's got it now

Yes but my other plant is not getting this issue. No stink bugs this year (I have ahd that happen). These plants might get a little more sun. That might be it though - no peppers with sunscald - but I have in the past.

Is sunsclad ONLY sun? Is heat involved at all? These plants are near a south facing wall that is black and gets HOT - so they get hotter than tomato plant that is ok.