Usually red spots on black come from bleach, as well. But, you say there is no way your clothes could have bleach on them. Just out of curiosity, are you on city water? If this was a one time occurance, maybe the city increased it's chlorine for a bit to clean out before winter sets in. Our city usually warns us first (so we don't drink it...not that you could, you can smell the chlorine, blech) BUT, then they totally flush the system and ask us all to run water at a certain time and they increase the flow, to clean everything out.