It’s marble. It’s a hard sponge you glued to the wettest area in your house. It kinda does that. But “pink” says pink slime mold, Serratia marcescens.

We get that pinkish stain (Serratia marcescens, which is is actually a bacterial biofilm) on our grout in the shower occasionally, but we have porcelain tile so I just use dilute bleach (i.e. Tilex). Not sure what one would do for marble.

Orange could be rust in the stone. But pink...yeah. Probably the bacteria. Bleach it. Test it in a less obvious spot first but just diluted bleach kills it and removes the stain.

If your marble is sealed, you might have to reseal? I dunno...

Picture with how old the shower is and if you know how it was waterproofed would help. It cold be a couple different things. There is a product called Poultice Paste that I know The Tile Shop carries and its made to pull stains out of stone. If you have some bodywash or shampoo that color your seeing its very possible thats what your seeing. Other wise it could be mold starting from the water not draining properly/voids under tile.