Are these chickenpox?

My 7 month old randomly came up with this little spots this afternoon, she does suffer with eczema sadly. It also have been very hot in the uk so I don’t know if it’s them or a heat rash? They’re only on her tummy and her back, she’s had a bath too and they looked the same than before and more haven’t popped up yet. I do also have a 5 year old who’s in school now but only been a few days