For some reason when kids slow down on nursing and are eating a lot of table foods they sometime show low in iron. Iron supp. by their self can cause teeth to stain. We use the Flinstone Multvitamin/Mineral supp and find it to work very well.
Minerals are almost more important to supp than vitamins sometimes.
I think in most towns the County Health Nurse will do an iron test for free, if you don't want to take him to a Dr. or something.
That is what we did and turned out our dd did have a low iron around one year and we brought it up with the vitamin/mineral supp.