Hard to see detail of the damage in that photo, but from what I can make out without a close-up, that looks like vole damage. Did parts of the plant start looking droopy and unhappy in the days leading up to this? If so, there are some diseases that will girdle the crowns of plants, and it might be one of those. If not, I would suspect a vole. Either problem is a big PITA, but the diseases that cause tomato girdling are much harder to eliminate than voles.

Thanks for the reply. I've never seen a vole, and I'll get a better pic when I can. The bottom looks like it's hollowed out and as you can see the inch of stem above that looked like it's just died. There's something going on, don't know if it's disease or pest. Only my black krims seem unaffected. 4th of July, Sungold, and Celebrity all have spots on the leaves. Thanks again

It's possible to have a vole problem and fungal/bacterial disease. Happens all the time. It's also possible to have more than one fungal/bacterial disease at the same time. That, also, happens all the time. The diseases that girdle tomato crowns don't generally have spotty foliage symptoms. But it's very possible to have one of those and something like septoria, early blight, bacterial speck, etc.

If you have a lot of cover, mulch, etc., you may never see voles, which look like large, fat mice. They're often diagnosed by the kinds of damage they leave behind and by their hole and "runways", i.e. paths they wear into the terrain, as they travel the same routes over and over again. They don't tunnel underground but do travel underneath grasses, weeds, and mulches.

Here is an image search of typical vole girdling damage on a variety of plants.