I recently put in tile and grout around my fireplace. I let the grout cure for several weeks, it looked great. I put some sealer on the grout and the sealer caused the grout to discolor. It is lighter now and blotchy. I don't know if it is a residue from the sealer - but I have tried scrubbing and scrubbing with soapy water but cannot get the grout back to its original color. The sealer is from Tile Lab - Grout and Tile Sealer. Any ideas?