I have a cockleshell orchid which had come in a pot. I mounted it about 9 months back. About 4 months back I removed a lot of moss around the roots, thinking that maybe there was too much moss. Lately though all the bulbs have started becoming brown. Any ideas what might be the cause?
I grow one of these in S/H. It had almost no roots when I put it in (but had a new growth just starting).
The new growth put down masses of roots into the wet environment of S/H and now the plant is really happy and putting out yet more new growths and roots.
I agree with Philip that these need a lot more moisture than yours has been getting and I think yours is struggling due to lack of water.
The coloration (especially in the 5th photo) looks more like rot to me. If it is rot then I would remove the orchid from its mount and cut away all the brownish material. Then I would select pretty much any other piece of wood besides cork to mount the orchid to. Cork is probably the least absorbent wood that there is...which is why they use it for wine bottles. It works well for people with high humidity though.
When remounting the orchid I wouldn't include any moss. Many orchids...especially those with fleshy pseudobulbs are like succulents. If you're trying a new species it's safer to err on the side of too much drainage. That way if it starts to wilt you'll know it's because it wants to be watered more often...not because the roots were rotted from insufficient drainage.