Shower 'stone' getting discoloration ('wet') stains - Tile Advice

[rclough1684]

I could use some help from everyone! The floor mosaic tile was recently retiled over a tile-redi base but the affected material (pictures attached) was not changed. The stone appears to be soaked or wet with water. I have a few theories about what could be going on here but could use input from those who are more familiar with tile:

• All grout in the shower was sealed. I've heard of sealers 're-activating' prior sealant solutions. Since I was intending to seal the grout, I wonder if the stone sealant could have been removed as I wiped the surface down around the grout lines.
• The 'baseboard' was previously just grouted on top. Since the grout fell apart soon after moving in, I grouted behind the big tile piece and siliconed over the top to prevent water from getting into the gap behind that large piece of stone. Perhaps moisture from the bottom grout is getting trapped behind the stone if the silicone is sealing up the top.
• Poor grouting in the corners. This seems unlikely since the prior grout was in shambles and likely allowing water to get under that stone.

The stone has scratches in it so I suspect it's marble. Any insight and guidance would be much appreciate, thanks all!

 

[Kastar UK]

Can you get epoxy grout in twin tubes in the US ?

 

[Tile Marble Granite]

It looks like it's not sealed. Let it dry 24h then reseal it a few times. That is natural stone marble.

 

[Dan]

Generally you tank/waterproof the walls before tiling. The tiles are then just for the looks.

Sealing them will work but can fail over time with using bathroom cleaners on them.

Marble and stone change colour when wet but they dry out fairly quick too. I don't mind stone changing colour as long as it had time dry out. It's stone its what it does.

6mm silicone bead only around the corners or where tile meets any other material type as expansion and retraction can occur.

Go down the sealer and silicone route now though. But might need strip and reseal every couple of years maybe?

I think @Kastar UK mught be able to help soon but it would involve international shipping but I think its basically the fix for exactly this? (Grout wise) impervious stuff @Kastar UK ?