Hi there. Wondering if anyone can help? We had a path laid using reclaimed quarry tiles on top of a new concrete base. It looked fine to start with, but a few days after laying, some of the black tiles started to show white haze / rings. I presumed grout haze so tried white vinegar and then a cement remover from Topps Tiles. Neither shifted it. So then I googled it and wondered if it is efflorescence, however it does not brush off with a wire brush and it comes back immediately after washing with water - so maybe not? I’m not sure what else to try. The tiles were laid about three weeks ago. Any other ideas welcome. Thanks.