Rash around diaper edge

curmudgeon

I haven't posted here before, but I'm thinking I may have an issue with our diapers.  We have used Smartipants for about 6 months, I wash in dye/fragrance free detergent, a little oxyclean, and lately have been throwing in a little hydrogen peroxide (helps with the urine smell).  DD has been developing red marks - maybe rash-like, maybe friction-like - around the edge of the diaper.  She has been having bouts of diarrhea but I don't think it's diaper rash because she has very distinct red areas along the thighs (primarily) and not in the areas where diaper rash tends to develop.  Any thoughts?  TIA.