This is more the rule than the exception at LFS's and is typical. Unfortunately for the newbie who may not know better these things may be purchased. There's little to no hope to raise this stuff to be healthy.
I understand that your trying to be fair to the LFS, but I can't say it's entirely NOT the fault of the LFS due to the fact that very few of them make an effort to keep the Discus in ideal or acceptable conditions often just throwing them into any tank available without regard to temp. requirement, in large group filtration systems that may cause them to get sick. Housing young Discus in tanks with any other fish in tanks that are overused and may have any number of diseases/parasites is very common. The low quality of C grade Discus that are also very often juiced is another contributing factor.