watering and fertilizing paphs

[Pokey49]

Figuring out the right amount of water and fertilizer for my paphs is a chin scratcher for me. I admit freely that I am new at this. I bought a paph back in December in bud and it has been open in bloom for a month now. I have been watering it once per week and feeding it with "orchid plus" ina 20-14-13 ratio. It has been doing fine, except now I see the two bottom leaves are turning limp and pale. Since I am new at this I have been checking the medium with a moisture meter until I get the hang of things and do not water unless it appears to need it.

What's going wrong? I don't want to keep repeating any mistake as I just got in 5 beautiful plants from Lehua Orchids in Hawaii. The medium in them is quite coarse and appears to dry quickly, have watered them twice now in a week. Would love to have some expert paph advice.

Thanks in advance

Paul