I've been buying powdered nutrients for many years from Alpha Chemicals and other suppliers (N, K, P, Sulpher, urea, ammonia, etc.) and mixing up my own batches with molasses, leftover beer from parties, etc. on my hostas, roses and other garden plants, but then again i have 40+ years of experience f'n around with garden plants. However, killing a rose at $30 a plant doesn't come anywhere close to comparing it to over nut'ing and killing a cannabis plant
, so i therefore know shit in this area, especially when it comes to the flowering phase, and in what you can use in order to maximize bud size and quality - and im way too afraid to try f'n around.
im therefore using half the recommended dilution of Miracle-Gro Bloom Buster (15, 30,15) every 2-3 days (i like it because it also contains trace amounts of zinc, boron, copper, molybdenum, manganese and iron, which are all needed micro nut's), AND, bud candy and big bud at their recommended ratios, and so far my girl is starting to look nice and plump - just the way i like all my women.
(that is not meant as a sexist comment, that is a personal preference.)
(And yes, as Rurumo said, the marketing ppl are targeting newbies 'cause they don't know any better, but who the hell doesn't react to an add that says: "Hey, want monster bigger and sweeter tasting and potent bud's? Guaranteed results in 24 hours.")