Rash on hips and back

Danielle

My 13 MO has a rash on her hips where diaper tabs sit and lower back where the top of the diaper sits. It's tiny bumps- not very red or irritated and she doesn't seem bothered by it at all. I'm just wondering if anyone has ideas what it might be? I haven't changed diapers- Luvs and Kirkland...no changes at all really! TIA