When my oldest son turned three I noticed that he had cavities in his
back teeth. I took him to the dentist and he showed me how those
teeth were yellowish/brown and told me that his enamel didn’t fully
develop on those teeth. Unfortunately, his were so bad that he
had to have surgery and both of the bottom teeth removed because decay
was so deep. The dentist indicated that some kids “just have that
happen” but also asked if I had a high fever at some point during
pregnancy. I wasn’t sick so just chalked it up to him being “one
of those kids”. I don’t mean to worry you but if it happens to be
something like that, if caught early you may be able to avoid having to
go through all of that. Good luck!