Abundance of Potassium isn't the only goal to reach to achieve fruit sweetness and quality. Calcium is also extremely important for fruit sweetness and texture, and also for branch sturdiness and disease resistance.
Soil should have at least twice the parts per million of Calcium, as compared to the ppm of Magnesium and the ppm of Potassium. [Many authors and consultants promote SEVERAL TIMES THE AMOUNT OF CALCIUM OVER POTASSIUM, and they are probably right.]
In many plants, DEFICIENCY OF COPPER causes weak lanky branches.
Although one is right to campaign against the traditional, constant over-use of Copper, many on this Forum have gone to the other extreme, and their plants now suffer from Copper deficiency. Copper is an essential micro-nutrient for plants, and for humans also.