Here's alittle info on K.
Potassium
Type: primary macronutrient
Necessary for formation of sugars, starches, carbohydrates, protein synthesis and cell division in roots and other parts of the plant. It helps to adjust water balance, improves stem rigidity and cold hardiness, enhances flavor and color on fruit and vegetable crops, increases the oil content of fruits and is important for leafy crops. Just as with P, K uptake is highest during the earliest growth stages. K is associated with sturdy stems and resistance to disease in plants.
Deficiency symptoms: Leaf margins turn chlorotic and then necrotic; scattered chlorotic spots often occur on the leaves, and these spots may later turn necrotic. K deficiencies sometimes show on indoor plants even when there is apparently enough supplied for normal growth. Often, potassium-deficient plants are the tallest and appear to be the most vigorous. Starting on the large lower leaves, the tips of the blades brown and die. Necrotic areas or spots form on the blades, particularly along the margins. Sometimes the leaves are spattered with chlorotic tissue before necrosis develops, and the leaves look pale or yellow.
High amounts of K can cause Ca, Mg, and N deficiencies. High sodium can cause K deficiency.
High soil Mg can reduce K uptake, but it seems to occur only when the soil Mg saturation is in the range of 25% to 30%, or higher.
Numerous studies have looked at the possibility of using the K/(Ca + Mg) ratio to explain certain nutrition problems. While this ratio may be useful at some times, often there is no relationship between these cation ratios and crop performance.
High K levels can help against ammonium toxicity.
There is no evidence that K has a direct elemental toxicity. Excess K is more likely to be experienced first as an induced Mg deficiency. Next on the scale of probable high K damage signs might be induced Ca deficiencies
Does this sound anything like what you have going on? If so up your P/K
Good luck
BHW