Since I would not be able to speak in such detail, accurate, thorough, fertilizers and fertilization guidelines based on years of experience and texts followed methodically by Piergiorgio Difilippo , I refer you to Acquaportal long article published recently in the beautiful shows the home page.
I can say I tried a few lines of products of different brands, but I never even entered my head to measure that way all-in-all.
(One might add that "sees", looking at the results of my last exhibition ... )