Hi we had a wet room tiled about 3 months ago. I hand washed the tiles down with fairy and water after a month as I kept spotting what looked like streaky grout dust marks is the only way I can think to describe it. However in the brief encounter with the sunshine we have had today I have noticed there still appear to be marks on the tiles. For all the world it looks like when the tiler wiped the grout a light film of grout dust has coated the tiles it's not rough to the touch and when I wet wipe the tiles it appears to go. Seeing it today however I clearly have not done a through job or not used the right product - any ideas?