That's the whole point of supersoil.. minimal input beyond what it provides.. if you want to be more precise or play mad scientist with the formula for different stages and whatnot, do soilless/hydro.
What did you notice the past 3 grows that seem lacking? any symptoms? or, maybe just want to try pushing boundaries? add a little more to the soil next time or buy somethign you can top-dess or slow release type stuff...
You could buy products like triple superphosphate (0-45-0 - also 17% of mass Ca) if you want to boost 1 of NPK etc. not sure if that falls under the marketing term, "organic." THat term as used for horticulural products has no place in science. it is not a science term as used by marketing/advertising of these products, and the science term is not very relevant to anything that goes on with caring for plants. The distinction in and of itself causes nothing.
E.G. CO2 is inorganic.. there's no such thing as an organic garden.. all the carbon comes from an inorganic source no matter what you do. The back bone of near every single molecule of the plant is from an inorganic... most of it's mass not counting water-weight, i bet.
Anyway, i wouldn't fear mixing non-organic products in as it makes no real difference. And, if you have healthy plants from seed to harvest, i wouldn't make and drastic changes... slow and steady wins the race at that point... test a boundary, and dial back if you have to or leave it and move on to next boundary to test.. somem of this stuff is relative to each other, too... try to limit what you change each grow moving forward to 1 thing at a time so you know its impact for best results..
don't thro a wrench into something that works well
;)