mayan disappearance theory

My theory is that the Mayans fled their city out of fear of a man-made plague called Anemia. Anemia is caused by lack of iron in the blood stream. This makes sense because 8O percent of the skeleton found in a city called Copan showed signs of Anemia. I have 2 possibilities as to how this plague came to be, 1. By sacrificing all of their important genes they created the disease. 2. they over farmed their land, by growing the same crop year after year they did not allow any time for the soil to regain it's nutrients, producing less crop each year.