I recently purchased a Zygo. mackeyi. Just the other day I noticed that two of the leaves were turning yellow and brown. I cut them down and then sprayed it with fungi spray. The next day the whole 2 leaves were yellow and brown. I cut them all the way down this time. It has a bud and three other leaves and I am afraid it will spread. Does anybody know what this would be? Could it be a virus? I have it away from my other orchids.
If the leaves are on one of the old, or back bulbs, this is normal. The older bulbs shed their leaves as the mature. If the new growths look ok, there's probably nothing to worry about.