Vinegar is one of the best mold cleaners I know. It kills the mold. Wipe down the tiles often to prevent it from coming back. Be sure it has not gotten into the walls etc or you could be dealing with serious health issues if it is black mold especially. We also find Simple Green works great to kill many kinds of fungus or molds.
Use vinegar, it wI'll kill the mold.
The best thing I have found to tackle this problem is baking soda, Dawn dish soap and vinegar. If that doesn’t work use straight hydrogen peroxide. Rinse well.
Vinegar or Bleach. Bleach will work on non-porous surfaces(like tile), but not on porous, like wood or wallboard.