Thanks. I now measured pH of 70% coir + 30% seramis, leached with 2 times pot volume of tap water (0,2mS/cm) and 1 volume RO. It is 6.3.
In my initial post I wondered if any charts exist for coir, thinking it might well be a bit different in coir compared to the posted chart which is for a specific mix. But there is one more variable I read about here
: How much available nutrient vs pH depends a lot on what molecule the ion is part of, if part of sulfate it is soluble at much higher pH than if oxide, it says.
Coir has the highest CEC of all potting mix materials per volume
, and what counts for potted plants is per volume not per weight. And as Bunt said, CEC mainly affects divalent ions, most monovalent ions remain water soluble.
Testing pH of fertilized soil might be a good idea. Due to Coir and my usual fert both being a bit high on K and seramis adding to the K I decided to add some Ca+Mg (an N), found a suitable bottle called "Magne-Cal". I should buy that first before testing.