According to who? You?
Point me to YOUR research.
Its basic physiology of how plants work.
If a plant needs 6 separate elements in certain amounts, and if you only give it 3, then it will still grow but will be held back a bit.
Similar, if you give it all 6 elements, but in wrong amounts, then also it will be held back a bit.
Think of a growing child, who needs 2000 calories a day to be healthy, if you only give it 1500 calories per day, the child will still be living but might not develop or grow as much. Similar, if you feed 2000 calories of just Coca-Cola or cheese, the child will have malnutrition and have problems.
About NPK, we are using some ballpark of 2-1-3, as far as scientific backing for this, the best thing you could do is a bit of research about cannabis NPK, there is quite a lot of research about it, it goes back over 40 years (those hippies were pretty smart!) Different strains/conditions have slight variations in what they require exactly and we tried to cover all the bases with that, including coco growing.
So, I've done quite a bit of research on this at school (I've got access to all the good expensive databases), and commercial growers start out with a base hydro nutrient and add extra stuff that's crop specific (fruiting is different than leafy veg etc). The base nutrient works but doesn't yield as much, because it has everything necessary for the plants to grow but not in optimal concentrations.
They also conduct water analysis of their feed water and change the formula to account for whatever is present in the water.
yeah, this is true. For commercial grows (think of like corn or wheat) the fertilizer they use are mega bulk type things like Urea, Ammonium Nitrate, Potash. These things are very cheap too, then they add some extra product to make it work better for their crop more specific.