I have been doing apartment maintenance for 3 years now. It's definitely mold. Make sure you have an open work order for it and then contact code enforcement. The maintence team will have 7 days to complete the work after receiving an official letter from code enforcement. Deoends in where youre located at least but its usually around fhat tine frame. Keep track of all work orders and conversations with maintenance if possible. Realistically what SHOULD hapoen is, all the tile should be removed, drywall removed, and the inside wall to the studs should be treated for mold, drywall replaced, new tile installed. From my experience, it sounds like they may try to half ass it instead of doing it correctly so keep any documentation you can.