I think this is actually more common than we think because breast milk is not "iron fortified" like formula. Most of the time, as unfortunete as it is, the standard for all babies and toddlers is based off of formula fed babies. Not saying low iron isn't a problem, but who is to say the standard shouldn't be lower than it is, KWIM?
So, first I wwould try to determine if my child had any symptoms of low iron... fatigue, low energy, cranky etc. My toddler had slightly lower iron levels then they sd he should. He showed no signs of anemia, so I simply increased iron rich foods, made sure he was getting vit c with those foods, and it is normal. We never supplemented with any type of vitamin.
I have a hand out on iron rich foods and ways to increase their absorption. If you send me your email, I am more than happy to email it to you. Maybe that will help! My email is ____@____.com
Good luck and you aren't alone! Another resource might be La Leche League... it was helpful for me in terms of anemia!
E.