you reading skills and comprehension are excellent
Tru that barked based media needs a higher nitrogen bec the bark eats it up and it doesnt get to the plant so you have to bump it some so the plant can have some too. This also causes the bark to breakdown and you to repot on a regular basis.
Moss and Granite chip users like myself can use a more evenly balanced fertilizers. I have been using Peters Cal/Mag which is 15-5-15-5-2. Calcium and magnesium being the 5 and 2 respectively. The nitrogen based urea is 2.05%., 11.75% Nitrate nitrogen, and Ammoniacal Nitrogen 1.2%.
You can use the Peters 20 20 20 and add about tablespoon of epsom salt to each gallon of water for magnesium and add lime pellets to the mix as a top dressing for calcium. You can use calcium nitrate also but its hot on the Nitrogen side and you wont need anymore Nitrogen with the peters 20 20 20.. You might not be able to find the Cal/Mag in smallish quantities bec this is a more greenhouse growers oriented type fertilizer and why I suggested the peters 20 20 bec it is readily available just about everywhere.
Your hardware store fertilizers typically dont add Calcium and Magnesium. Your orchids need these elements for healthy shiny leaves and strong fibers