Oh, Jerry that is so cruel.
I think the staining is from the top side. Maybe repeated cat piss or some other leak. Those cabinets look like the HD unfinished oak type that you install and then stain to taste ... maybe they spilled the can of stain?
I doubt it's coming up from the slab, just doesn't fit from what I see. Besides from your posts, I'd say your good enough to have found a slab/water problem if it was there.
Stop laughing Jerry.

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Markus Keller