M.S.
Likely could be caused by antibiotics, especially if in the Tetracycline family. Go to drugs.com and look up Tetracycline. The very first warning, not to be given to children under the age of 8 because of the TEETH discoloration. Also not to be used in last half of pregnancy for same reason. Too bad, when you see adults with gray teeth, it was often caused by Tetracycline used when they were children, very often used when couldn't use Penicillin drugs..