Talk to Pediatrician on Diaper Rash

Baby age 26 months Birth weight 2.3 kg Current weight around 10.5 kg

Baby had severe dirrhea for about 10 days a few days ago. Now she is fine Alhamdulillah. She developed a rash twice during this time. The rash was reddish and was evenly spread it was cured by using a combo of sudo cream and olive oil both times. Now that rash is gone but a black tinge is remaining on the area. I stopped using the combo after redness was gone. Today I noticed reddish pimples around the area. Should I take her to a skin specialist or use some other cream. I change her diaper as soon as it gets soiled. Otherwise after every 3 hours or so. Kindly advise.