Hi, just grouted my bathroom but have noticed that lines are appearing in the grout perfectly center between adjoing tiles. From a previous thread i saw that it is because im using a ready mixed adhesive and grout formula from Wicks which is bad. I decided to use it only because i did not want to waist; i have the powder so no probs there. My problem is what to do about the defective grout in the tiles. Do I have to scrape it out or can I simply grout over it???? Its still drying so if someone is there an immediate reply would be good.