Any suggestions on what it could be?

(First picture) So we woke up this morning, changed her as usual nothing different, we went to drop daddy off, hung around for a couple hours, we got home, I noticed it till the afternoon, she hasn’t cried all day nor seemed bothered..

(Second picture) she got this about a month and so ago, it started like this looking like a burn or something like that and ended up peeling and looking like the first picture, it just kept peeling off and with a couple days it went away, a couple days before it totally went away she had a ped appointment and her doc just said “babies skin is sensitive they get stuff like that but it’s normal” it was already going away and she didn’t seem bothered by it at all so I just thought it was normal, but now she got it again 🥺🤔