Do you think this is an allergy or a dribble rash?

Hi, Looking for an opinion. Son has cmpa and is on Neocate, but hasn't had a rash before. He dribbles a bunch and had a few spots around his mouth/chin, but now they seem to have extended? They're on the his neck as you can see in picture, and no other spots on his body. Having a tough time figuring out if they are a reaction to some ingredient as he's been going to nursery a couple days a week, and it seems to be worse when he comes back. He is on solids and gets dairy free solid food there as well. But they might also not be as diligent about drying his neck and he's drooling all day. Any opinions?