I left HG Scale Away on ceramic tiles slightly too long - about 15 minutes. I was scrubbing away at hard to clean areas, that took ages to get off. It has left a white residue that doesn't come off if I scrub with water. I'm really hoping this is residue left on the tile (it looks this way) that can come off with the right product, and not some of the print rubbed off the ceramic tile. Does anyone know a good product to deal with this?