Fruit trees here need some nurturing for their first decade. After that they do amazing in their growth getting much larger compared to commercial fruit tree orchards, but will continue struggling to produce fruit until you give them potassium. With a large potassium infusion in the last spring you can get some insane harvests. My solution for potassium is cases of over ripe bananas blended into a puree, including the peels, and dumping into ditches around the trees. Then cover the puree immediately so that none of the moisture can evaporate.