In most cases, it looks like your bean sprouts have become moldy, but they have not developed any mold. What you perceive as mold is actually fine root hairs. These fine root hairs look similar to mold. If you begin to see root hairs, it as a sign that you need to rinse them. You should not keep your bean sprouts in the cabinet either, as it creates a very humid environment for bean sprouts to grow. You can differentiate between root hairs and mold by smelling your bean sprouts. Mold has a peculiar smell, so you will know right away that you are dealing with mold.