I'm stocked... managed to source Compo's Hakaphos Basis 4 (4-16-32) +6 and Multi MKP from Manna (52-34) from Duengerexperte (great service!).
Thanks c64 for this thread, and Absolem for the advice on the canna a + b schedule thread, and of course to everyone that chimed in with advice or where to buy:
Already had Yara Calcinit and SOP, next reservoir on my big tent will be 100% salts, used Canna A+B in veg, Canna A+B plus SOP on first flowering week.
Lowering PH with Nitric acid. From my limited understanding while reading this thread and others, (still learning) seems to be the best option in coco for carbonate breakdown, PH buffering the medium and preventing Ca/Mg deficits due to too high P ratio issues which on my conclusion is a drawback one should look after when using coco medium.
I've noticed a definite enhancement after switching from Phosphoric to Nitric Acid as PH-.
Now deciding on which soil PH meter should I get... will be used for my orchard and vegetables garden too.