Limit the amount of seeds offered or sprout them, and increase the amount of fresh foods. Offer lots of green leafy vegetables, less corn, more squash, carrots, etc. Limit fruits, as they contain a lot of sugar. Offer a variety and, as an enticement, sprinkle chopped walnuts or almonds over the top to get the bird to eat the healthier foods. Offer all of the food groups, with modifications for different species.
Sesame seeds are a good choice as they are high in vitamin A and can be offered in the same way.
They can be found in most health food stores in bulk. We feed twice a day and check water more frequently. The wet and soft foods go into one bowl, dry foods in another. You should invite your birds to snack with you as well as offering them a bowl of their own when you sit down to eat. You will learn that birds love tacos, a little melted cheese, lettuce, tomato and meat served in a taco shell.