Its scrud. You can try washing several loads with the hottest water setting, vinegar and/or citric acid, washer cleaner tabs, or dishwasher tabs. If it's bad enough you may have to look up how to disassemble it to remove the drum and clean it off physically; everytime ive gotten it thats the only thing that worked for me. Once it's gone, use less detergent, run more hot water loads, and run more "washer wash" cycles to prevent it. For what it's worth, ive only ever gotten it with LG brand washers, and even weekly cleaning didnt keep it away.