Some fixes you can try:
Warm rinse instead of cold. This way your water is already running hot when it goes to the wash cycle. Otherwise, it may only be getting warm, and not hot by the time it fills up. Does that make sense?
Do a rinse and spin, so it gets rid of all the nasty rinse water.
Use more detergent. When you have hard water, you need abut half the amount you use for a laundry load. Not the skimpy 1/4 amount you read about some places. That's more for soft water.
Use the wet towel trick others have mentioned, or put it on extra water if possible.
I ALWAYS have used a toilet sprayer on my diapers, even with newborn poop. Otherwise it's just icky. I've never had stains. Blast it all off before tossing into the pail.
Hope that helps!
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Mama to "The Fantastic Four":
DS 02
DD 06
DS 09
DD 12