For set in mildew stains on fabric, mix cup household hydrogen peroxide with cup Clorox 2 powder. Stir into a paste. Apply to mildew stains. Let sit for hours and rinse well. If there are still stains visible, repeat till gone.
Your bathroom makes an ideal breed ground for mildew due to the high humidity and constant exposure to water. Unsightly mildew stains make your bathtub look unclean. Clean mildew stains sooner rather .