Iron Drops Stains

Does anyone have good tips on how to remove iron stains from onesies? I didn't think about it the first couple times I gave them to her (and of course it only ever gets on your favorite ones) Now I strip her to the waist before trying to give it to her, and I'm better about pacing it so she's less likely to push it back out, but the damage is done.

Also stained the changing table cover and a couple tri-fold cloth diapers but I'm not overly worried about those. I use the tri-folds as burp cloths mostly... I was going to try hanging them in direct sunlight to bleach it out but I don't think I can do that to the onesies without fading them...