My little one just went dentist one of his tooth is a bit yellow they said just natural food staining
My sister had this and the dentist said it was something to do with her being unwell when the tooth came through. The mark couldn’t be cleaned off and wasn’t anything to do with type or amount of toothpaste used or anything like that. I’d speak to your little one’s dentist and see what they think 😊
I have the same problem
Apparently it’s food colouring