A few months ago we installed slate tiles around our bathtub/shower and we sealed them with 511 Seal & Enhance (by Miracle Sealants) .
Since then we started to notice notice some areas of the slate greyer than others (attached pictures). Should we apply more sealer over the whole tile again ? or we should clean the whole tile and re-apply sealer?
We are worried that we may mess up the tiles more than what they currently are.