Once a month, add a cup of Distilled White Vinegar & 1 Cup of Baking Soda directly into the drum and use HOT water for washing. Then, I add about ½ cup of vinegar into the fabric softener compartment and ½ cup of baking soda into the detergent compartment. Set the wash on “Quick Wash” with HOT water and High Spin Cycle. If the mold situation is really bad,use bleach instead of vinegar and baking soda. But make sure you run a few empty cycles just with hot water before doing a load of wash.
Over time, towels build up detergent and fabric softener, leaving them unable to absorb as much water and smelling funky. Recharge them by washing them once with hot water and one cup vinegar, then a second time with hot water and half cup baking soda. This strips the residue and leaves them fresh and able to absorb more water again. Works like a charm!