Hi @Philip_Reck , I agree with your assessment. Excessive K is your primary limiting factor.

Foliar applying magnesium is an effective solution to address the systemic magnesium deficiencies.

In addition, I would suggest maintaining very high rates of manganese in the leaf with foliar applications. This will regulate potassium absorption.

Would it be possible to grow some high K requiring crops, like potatoes, to remove some of the K from the soil profile?