I have blue faux (cultured molded polymer) marble in the bathroom. On this I placed a ceramic tray which has a white unglazed base. Beneath the tray there is now a white cloudy area exactly the same shape as the tray. It looks like the base of the ceramic tray somehow bleached - or leached the color out of - the faux marble surface. What has caused this white clouding, and how do I get rid of it?