Rash on LO

My son is two months old, I took him into the pediatrician for his 2 month check up. At this time he had a little rash on his neck and belly, she thought it was just dry skin so she told me to put Vaseline on it. We also had to change his formula to a hypoallergenic one, but he had this rash before we switched formulas. It’s been 2 weeks of putting Vaseline on it, and it’s not going away. Can anyone tell me what these rashes are ? There’s one on his neck and one on his belly.