"The third, I use it as my MAJOR fertilizer for the parvis, delenatii, armeniacum, micranthum and malipoense ( don't do that on emersonii or hangianum, or they will look really, really funny !)."
What is your reasoning for using a "bloom boost" as your "major" source of nutrients for the mottled leaf parvis?
There was at first no reasoning. I watched my plants in a bark/cocofiber (the old trouble-free material sold years ago...), Dolokal lime ( 5kg/m3 of potting mix), and PG-Mix ( 5 kg/m3 too... slow release fertilizer). The two latter were mixed with high quality peat before being added to the 75:25 bark:cocofiber mix ( it is not CHC, well, it looked a little bit like that, but irregular, nearly black and spongy material, I will make posts later about the CHC and how to use it foolproof in all cases, I am just waiting for a patent to be granted
I use for all my plants, no exception, a 10-52-10 fertilizer after repotting. It makes very nice roots, very quickly ( spectacular on vandaceous as well !). I noticed that those mottled leafed paphs ( I forgot to mention, vietnamense does NOT like it at all !!!), delenatii, micranthum, armeniacum, malipoense, jackii, and all the brachys (I can confirm, thaianum as well !) had a very fast growth spurt after "repotting" and each time I applied that 10-52-10 in my fertilizer schedule. So I decided to go for a mostly 10-52-10 feeding schedule for that group.
I found it works wonders as long as the potting includes carbonate ( calcium carbonate is perfectly fine), and as long as the plants are supplied with extra micronutrients. Micranthum will mature a growth the same year it is initiated as an example... I will explain more on that later, and why it works. It took me years to find out why it works so well...
I did the soil analysis, but I type slowly, many papers to compile too to write that ( and putting on the forum forces me to do, I planned to write a complete paper on that, but was too lazy, or busy to do !!!)
Definitely the fern roots, leaf mould and the like are a very good source of nutrients for the paphs. I have seen really great paphs in ferns roots ( not tree ferns, but really asplenium and the like roots !) and leaf mould, and some type of sphagnum ( for that purpose, our European sphagnum is better than the NZ sphagnum, and I got a similar one from Viet Nam too). I have the analysis including for 3 different sphag, so I will put these online later.
But all of those mixes are "bad" too in the way that first they cannot be international ( chilean sphag moss as an example is very different from the NZ one or the whatever one people can have locally...), and second, they cannot be standardized for cultivation of a very large quantity of plants, at least commercially ( who would sell leaf moulds or washed asplenium roots those days ?). That's why I tried to find the way to make something "standard".