i recently had new tiles laid on my toilet floors. however, they look kinda dull with some stains, probably from dried cement/mortar during the installation process. i've washed the floor twice already and gently scrubbed it with a sponge and floor tiles cleaner but it didn't work. my contractor wiped some chemical on it but that didn't work either. any suggestions on what i can do? i've heard of doing a chemical wash. would that help? thanks for your advice!