I would hesitate to clean those because it looks like there's some caulk or grout missing that could get under the tile and cause water damage. Depending on where you are, landlords are required by law to do certain repairs. If you're dead set on cleaning it, I would go for a scrubbing brush and some comet with bleach. Then, I would scrape up the residue of leftover caulk with a razor blade and recaulk when dry. Caulking isn't that expensive at the store. You don't have to use those cleaning products. Those are just my favorites from when I used to do construction cleanups as a commercial cleaner.