adespo,
Welcome to the forum!
I read many threads before joining as well. The members here are really good at making you feel welcome and answering your questions. Hope you enjoy your stay.
As for the residue on your leaves. It is most likely a residue from dissolved solids in your water like calcium, iron, etc. Do you have especially hard water? If you do, you might think about using different water because a build up of salts and too much minerals can cause problems.
jay
p.s. We love to see pictures, and if you have 23 orchids you are bound to have some good pictures to share.
