If you are anemic but have normal B12 and folate (folic acid), (folic acid) could there be another nutrient related to folate (folic acid) or to B12 that is low?

Well, sure. Iron deficiency is the most frequent cause of anemia. If you have already been checked for that, your provider needs to look at several other things not necessarily related to nutrition to determine the cause. Don't just take iron, though, unless your tests show that it is deficient.