If I listened to hydro guys I'd be growing with all AN gear. The shops love to push that stuff, it's full of high-price nutes, tons supplements/additives and they make more $$$$$$ selling AN. I'd like to see that mag they gave you, it'd be interesting to see what they say about Canna... but yeah, AN don't have the most honorable business practices.
Either way, the stuff I have is great, it's made of fermented plant extracts, and because it's plant based my girls take up the nutrients faster.
I like to use this link as a reference, b/c ODA are serious about the cannabis that is produced medicinally, and they will not have anything that isn't legit. The majority of the nutes on the list are there because they unregistered products, as in they refuse to tell the public EXACTLY what is in their shit. Also, mislabeled products, i.e. they say it's organic but it's not.
http://www.oregon.gov/ODA/PEST/stopsales.shtml
edit: let me reiterate I'm not trying to be negative, this is just what I've gather through research and experience.