Went to a job today, business as usual. tiles were substantially dirty and it came out great but as it started to dry, the grout formed a white residue..i used an alkaline cleaner (grout master).. this has never happened to me before. I am not sure how to rectify it... acidic cleaner? neutral cleaner?.. i told her i stand behind my work and i would go back if it didnt subside.. but not sure whats going on.. any suggestions?