Once a month, I add a cup of Distilled White Vinegar & 1 Cup of Baking Soda (adding both neutralizes the pH but the bubbling action gently scrubs any debris you can’t get to inside the drum) 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.
How to get your dirty whites clean again... HOT HOT HOT water, 1 cap of laundry detergent, 1 cup powdered dish washer detergent, 1 cup bleach, 1/2 cup borax. Tell you what, you have to rewash it once to put softener in but it's the whitest you'll ever see your whites. If you omit the bleach it works great to get stains out of colors too (baby spit up is no longer a stain on OLD clothes)