I usually fertilize with Peters - I use a balanced fertilizer like 20 -20 -20 during regular growing season ( mostly Summer outside and once a week)
In Summer I also add Magnesium Sulfate once in a while ( Epsom Salt) at a teaspoon/gallon. It helps keeping leaves green.
I switch to fertilizer containing higher levels of Phosphorus as in 10 -30 -10 or even middle number 50, when ready to bloom. ( mostly inside about once a month)
At least that's what I aim to do, but my schedule is not written in stone. And I always spray the whole plant.
Here is a good list showing which ones of the Phrags and Paph species need the Calcium additions.
http://www.slipperorchids.info...
