What is this!?

FarmWife 🌾 • 2015 👧🏼 2017 👼🏼👼🏼 2018 👧🏼 🌈 2020 👶🏼

My 3yo complained of a sore butt yesterday and I put cream in the crack. Didn’t notice this rash before. This morning she said again my butt hurts so I went to put cream on it and she had this large rash.. it’s more red right now cause I had her soak in the bathtub. This morning I put aquaphor in it.. any ideas? Maybe from wet pull-up? She typically doesn’t wet them anymore, but every now and again.