OK, I need some constructive instruction. I did a polished slate floor in herringbone, and wanted Black grout to accent the colors in the floor. Well I’m having problems with efflorescence/gray grout. I know I really screwed up by using to much water to clean the tile, I don’t know how I could have avoided it tho. The tiles are 3”X12” and the amount of cleaning was unavoidable. I have done black grout before this and did not have this problem. I used Mapei un-sanded grout. I’m not a fan of how the Mapei grout refresh looks or feels, so I’m not a big fan of that solution. And using an acid to clean the grout with not work with the natural stone. So what can I do to fix this with out completely removing all my grout, which I do not want to do(because I would have to polish and reseal the tile before grout again)? Do I have any other options?