Hi We Have A 5 Month Old We Thought She

hi we have a 5 month old we thought she had a diaper rash it red and peeling but it also has a smell to her vagina she put her in some water to take a bath and when the water touch her she screamed and she also has small bumps on her buttocks can this be a yeast infection we use baby wet ones to clean her good inside after she have a bowel movement