I was trying to find some supporting documentation of why I feel it's high P. I don't doubt they were over fed at some point.
Phosphorus excess
A phosphorus excess affects the plant by causing a massive nutrient lockout of other elements like calcium, copper, iron, magnesium and zinc, being zinc the first micro-element to get blocked. In this way, we must check for deficiencies of other elements to correctly diagnose a phosphorus excess and to know how severe it actually is.
If we detect an excess of this element we should flush the roots with at least three times of water than the capacity of the pot. There are products to break down salts to ease the flushing of the roots, which should be always used with an adjusted pH level depending on the life stage of the plant.
Zink and iron are immobile. Also notice the tip scorching in new growth
