?

I moved into and apartment with mildew stains on some of the shower grout. There is no mold or mildew. The shower is clean but I can’t get rid of the stains the mildew left. I have tried a few bleach products, vinegar, baking soda paste, Arm and Hammer “scrub free” tile/grout cleaner and every solution Google could fish up for me (well with in reason) including rubbing bar soap on it.

Does anyone have a good way of getting rid of these stains short of ripping out the tile?