If you haven't bought the gro and bloom yet, try to get their Foliage-Pro its for tropical plants also 3-1-2 npk supposedly its the magic bullet for weed used in both veg and bloom. will be trying it myself after im out of gro and bloom.
As for additives i just use Protekt by Dyna. Its a silicon additive, helps with heat and drought stress, strengthens cell walls for stronger stalks and whatnot.
Sterile vs non-sterile
bleach, pool shock, dutchmaster zone, h202 all can keep you sterilized use separately. Or go the live rez route. find what works for you and your system. I use Botanicare Hygroguard, Pond-zyme with barley and having good results.