You can certainly use flake and pellet food for Discus but they will not grow any where near there full potential. As for the frozen bloodworms get the Hikari brand because they do not have parasites. Ryan the breeder I get Discus from has been using that brand for 3 years and hasnt had a problem. If you want to make Beef Heart than here are the ingredients. All you have to do is grind it all up in a meat grinder and then add the gelatin and wet substances.
Beef Heart, baby spinach, wheat germ, knox gelatin (can be hard to find as it is in a tiny box). You will also need 1/2 banana, 1 egg yolk (yolk only, no white, ask your mom to separate the yolk for you) a can of flake food and some color bits.