Baby acne, heat rash or reaction?

So I'm out of town at the moment and debating if I should just get this checked out at urgent care. I thought a couple days ago it was just a mild case of baby acne but it has gotten worse. So now I'm wondering if she's having a reaction to the new formula or something. Anyone have some insight or things I should try? I think I'll be stopping the formula just to see if that changes anything.