Not saying your LFS is TRYING to deceive you (also not saying they are not) but I can say for sure that many stores that are not primarily "reef", like pet-stores that just happen to have a saltwater section, tend to not have a very good base knowledge of treating fish diseases. Their expertise ends in what helps them to move fish quickly out of their systems and into our tanks.
If fish get sick...then they can sell you 15 different "reef safe" remedies. If they die, well then you'll come back to buy more fish. Many of them don't know, or care to know, the intricacies of how to cure anything at all beyond reading the labels of the medications they stock, which are often little more than clever marketing hype. Besides that, if it sounds too "hard" they might not be able to sell you the fish in the first place... just something to keep in mind. The truly awesome LFS are few and far between...