Ive been feeding my Discus with flakes, frozen brine shrimp, and frozen blood worms, but they are a little picky right now and only seems to like blood worms. When I feed them flakes the would eat it but sometimes they would spit it right out and the same with the brine shrimp. What should I do to make them eat flakes and brine shrimp as I want them to have a variety of diet not just blood worms..