I have brilliant white tile in my bathrooms that is only 4 years old. It looks new except for the grout which is stained and dingy. I have tried every cleaner recommended and none work so I think the staining is permanent. In addition, the water turns grout blue/green in a day or two. I'm thinking of replacing the grout with epoxy grout. Will this work in the shower? Will it stay white and not stain? It's an expensive job to have done so I want to make sure it will work before I go ahead with it. Thanks.