Bill V. & others- Help! Dark spots on new tile and grout?
We are having some real problems with dark spots on the floor of our new shower. Background- Marble tile, unsanded grout, Schluter Kerdi system, floor was sealed before first use, been using the shower for approx 6 weeks.
Almost as soon as we started using the shower, we began noticing that the grout in some areas was darkening a lot and also not lightening back after 24 hours, even with a fan. It now has lots of dark spots (especially around the drain) and looks mottled in some areas. It also looks like the tile itself is darker in those spots where the water hits most often and there are some cracks in the grout, though not everywhere. It continues to get darker the more we use the shower.
The worst part is that this is the second time we have had this exact problem with this same shower, tile, and grout. The first time our contractor subbed the work out and the guys were not the best, so he assumed they did something wrong (plus they didn't use Kerdi that time and they didn't seal it), so he ripped it all out and redid it. That was about 6 weeks ago and we already have the same problem but no idea what is causing it. Please help!
This pic is right next to the drain