Personally I NEVER advise anyone to feed beefheart, its disgusting stuff and about as far from natural as a food can get (how many cows are discus likely to be eating normally?!).
The only time beefhearts likely to be any good is for big breeders on a mass scale trying to force young discus to grow at a really fast rate so they can be sold for more. It doesn't do them any good in the long run though and puts a huge strain on the filter. Discus would rather have good water than beefheart.
I always raised my discus on Prima or GranoDiscus and a LOT of bloodworm mixed up with brineshrimp/artemia, black mosquito larvae and greenfoods. As they got older i added in Krill and Chopped Prawn and as adults they ate whole prawns. Made feeding cheaper.
I made my own frozen food blends as it stopped them being fussy, fussy discus are poor doers. I bought big slabs of brineshrimp/artemia, mysis and bloodworms and a bag of prawns. heated it in a bowl over some hot water and mixed it all up, chopped in slithers of raw garlic (great for health and parasites and they love the taste of it) and also chopped spinach or sheets of nori seaweed for their vegies.
I then lined a baking tray with two layers of clingfilm, poured the mix in and spread it out until it was well mixed and flat, stuck it in the freezer, when frozen i wrappd the new slab in clingfilm and each day i just broke a little bit off for them.
By adding in the greens and a bag of frozen cooked and peeled prawns, it made the food go a long way for the money and if your fish have preferences, just change the recipe!