Black stains on diapers... mildew?

[KSDoulaMama]

I've just washed and put away a load of our diapers and I noticed several of our prefolds have blackish gray stains on them. It looks like mildew to me... Has this happened to anyone else before? Will it hurt my daughter?

We use a dry pail, wash diapers every other day. My daughter is 3 weeks old and EBF so we have not been rinsing the diapers before throwing them in the pail. We have an HE front-loader and wash first a quick cold cycle with no detergent, then a hot cycle with detergent, and the prefolds go in the dryer.

Suggestions?

[zwickya]

I don't have an answer, but I wanted to let you know I've had something similar. We have one prefold with dark gray spots on it. The spots have been on this one prefold for a couple of months. I just keep using it but always feel a little uncertain. It doesn't look like any of the other stains on our diapers. I don't see how it could be mildew after all these washings, but I don't know what else it could be. Our washing system is the same as yours. Anyone have ideas?