I am in the middle of a project, am putting down granite tiles for my kitchen coutertop. My problem is this, I'm using a sunset gold granite tile (light beige), 12 x 12" have set them with a premixed white thinset, couple of hours later the tiles have a blotchy grey discoloration on almost all of them. will this go away when the thinset dries fully caused by the wetness or is this staining the tiles? Should I have sealed the bottoms of the tiles before laying them? Also is the premixed ok to have used?, a friend said the latex in the premixed can cause the problem. any help would be appreciated.