Rash on 19 day old

So my baby has this rash on her but it isn't all over her, just on her chest- I noticed it over 12 hours ago and it hasnt gone, it's not raised or blistered, it goes if pressed.... we haven't changed washing powders the only thing we've done differently was use some baby oil in her bath on Monday night but I would have thought it would be all over if that?

Shes fine otherwise 🤷‍♀️