Bumping this because I’m interested in the responses.

It will be stone dependent. No general rules.

We have not seen so far with Taj Mahal (18 months).

We do have those stains / marks with Mykonos quartzite. Installed for a year.

I had no issues with my Taj Mahal slabs, although I did recently notice a touch of the darkening around the through-the-counter soap dispenser, but I was having problems with the soap dispenser and I don't think the hole was sealed after it was drilled.

I also wouldn't consider most of the Taj Mahal that is available these days as "white" or "mostly white". Once in a while you can find a creamy off white batch with brown/gold/rust veins, but those slabs get sold immediately. Most of the TM being quarried is more of a tan/taupe/gray.

@megs1030 Do you have any pictures of the stains? Any luck getting them to stop growing?