BM stains reappear over time?

bleu928

I had a good system for getting out BM stains with DS when he was nursed. He spit up a lot so everything had to be treated. I know for sure I cleaned everything before storing it for our next baby, but bibs and onesies have all of the BM stains on them again!  Tips on getting these old, reappearing stains out? 

ldcoffel

maybe wash and sun them while wet.