What could be causing this rash

Bri • Married and mother to babygirl💓

My baby is almost 6 months old and she has this rash . It’s up her back and a little bit on her arms . She also had eczema but this looks different . She eats solids but nothing out the ordinary these past couple days . I can’t imagine what it could be and I’m a ftm . Any ideas ? I just gave her an oatmeal bath tonight with some ointment so hopefully that helps