Not Eating

So my son is small he weighs 21 pounds and is a year and a half next month. He is low on iron and is taking vitamins for it. He doesn't eat... I make him good healthy meals and he refuses. He eats breakfast witch is always a banana smashed in his oatmeal some Cheerios or other cereal. Sometimes daycare can get him to eat but and home he doesn't. Is there anything I can give him to help him stay nourished and healthy? I am the organic momma if you will. So any low sugar organic magic drink out there? I feel like I'm failing him.