Help! - darkened shower floor grout
Our issue is one of darkened grout lines at the edges of our shower floor tile in a newly remodeled bathroom.
After using the shower only twice, we've noticed a persistent darkening of the floor tile grout near the walls, even after many days following the last exposure to water. Some of the darkening dries out, but some does not.
Since we're in Massachusettts, the shower was constructed with a flat copper pan then sloped mud in the pan, followed by porcelain mosaic tile with TEC AccuColor Sanded Grout mixed with Boost stain additive.
Our tiler was recommended by Bill Vincent and has indicated that discoloration like this can be normal. Before we accept the work of the tiler, we'd like the opinions of others as to how concerned we should be. Will this lead to mold problems or otherwise compromise the integrity of the constructed project? If it is not acceptable, what are the remedies?
Thanks for any advice.