See thats the thing, you and UB didnt actually explain shit. You's rode in on your high-horses, pointed to some generalised farming articles (and UB's apparently "oracle"-like brain), with nothing regarding the cannabis plant specifically and then UB pointed to the very products he was riding me for (high PK flowering nutes/additives)...?!
This is what you (along with many others), haven't got your brain around. Forget *cannabis specific*, that's pretty much bullshit. Generalised farming is pretty much all it is, all it ever was, and all it ever will be. Getting inexperienced growers to believe mj is some sort of special needs plant, needing special nutrients, special water, special whatever, along with a good dose of pixie dust, is what sells all this overpriced shit.
ANYWAY: To the OP, additives are by definition not necessary (if you buy balanced base nutes), but some of them can be helpful (as Im sure some of them are a sham).