I don't have a lot of orchids but I use neem on every plant I have, it has both fungicidal and insecticidal properties; it is my go to spray. I suspect hard water deposits are harmful in themselves.
Patty, I understand your hesitation, I killed a large and favorite plant of my mother's once when I was a teenager. I put it in the shower to wash the leaves and used cold water. I figured warm would shock the plant but it turned out to the the other way around. Every leave fell off the following day. This was almost 60 years ago and I can still see my mother's face when she saw her naked plant.
