Proper nutrient levels are the backbone of any grow cycle. When you balance the ratios of deliverable nutrition, you optimize the plant’s overall uptake ability. Nutrient uptake is not a singular element by element event. Even though there may be abundant Phosphate in the soil, not much will uptake without Calcium levels. Deficiency of Boron is directly related to Magnesium problems, even though there may be sufficient Magnesium levels. The soil requires more than just NPK, and if only NPK is used your soil is going to run out of vital “copilot” nutrients and suffer significantly from minimal production.