Try an internet search using either "pink mold" or if you want to get more technical, "serratia marcescens", coupled with "marble tile in shower".

See if that helps out.

I'll go in the opposite direction and have you consider that is wasn't the wrong type of cleanser or sealer, but instead the wrong stone that was used. While I love marble, is is porous, and some marbles often cause trouble in showers.

I don’t know about marble turning pink and I can’t see the pink you are referring to but it sure is beautiful!
FWIW, I have 2x2 calacatta gold marble on my shower floor and it’s been 7 years with no problems.

Where is this in relation to the shower drain?

The pinkish tile is towards the ceiling, away from the drain.

" The pinkish tile is towards the ceiling, away from the drain. "

Is this wall or floor tile? Picture of the hole shower?

It’s wall tile.

That is not good. Is the ceiling drywall that is painted? Or is it tiled? Is there any chance there is a leak (roof or plumbing) above this bathroom? That pink bacteria grows where it has been wet.

Yes, the ceiling is drywall and painted. I don’t think we have pipes running above the shower, but I will ask. Thank you for the suggestion!