I would feed them frozen brine shrimp (Live if you hatch it yourself), frozen bloodworms, discus granules, discus flakes etc. Most quality discus foods are great for a staple. You want to go frozen over live as live foods tend to caryy diseases which would likely cause problems in your discus. But raising your own live food ensures there are no problems.
if you feed frozen foods, you should thaw them out first. you may also want to rinse it in a net and only add the food to the tank. adding all the "juice" can mess with water quality if you feed a lot.