Is this baby acne, milk rash or heat rash? Few pics attached. Do I leave it to heal or apply something on it?

Did you shave your baby's hair recently? It looks like cradle cap to me because one of my friend's daughter had cradle cap and it looks like your second photo. Cradle cap can extend to the eyebrows. My gal has cradle cap too and I use olive oil on her scalp to remove it. But i suggest you bring to PD first to confirm what is this rash.