Food Allergies Treatment

My 4 month old daughter has a diaper rash where it looks like the top layer of skin has burned off in some places. It’s not too bad but I’m still concerned. Her stool is a little runny with tiny lumps in it. She has been on this formula for a little over a month but I know allergy’s can build up over time. I let her eat about a tablespoon of organic rice cereal about 3 days ago. I also bought her some new diaper wipes but they say hypoallergenic. Do you think it’s the wipes or the formula. I’m almost sure it’s the formula. The brand is Baby’s only organic milk based.