Aww mama, could be heat rash talaga especially ngayon mainit, or it might be something like baby acne na lumabas bigla, a few of us noticed yan sa aming babies around that age, sometimes walang clear reason! Since it's spreading and baguhan lang siya, best to show it sa pedia mo para ma-confirm kung ano talaga at ma-rule out any skin irritation, kasi baby skin is delicate and sometimes need proper guidance lang.