diaper rash help !?

So about a week and a half ago we introduced baby to reg similac to supplement breast milk, and about 5 days ago I noticed she has a diaper rash that has been lingering. Is s little bumpy and is all over ( where poo goes which is everywhere) but seems to be getting better with cream. We also switched to huggies one and done wipes from pampers because we have a jumbo box given to us...... I will take her to doc this week if rash does not resolve however just wanted some opinions on if anyone thinks it could be from change in food or possibly the wipes ?  I feel so bad for her ! Any experience ?