Question
Wayne, I have a large Vanda colection, basically all going well untill suddenly a good portion of my vandas are starting to drop the first (oldest)2 leaves. What could be the reason?

Answer
Jurg, it is not unusual for orchids, including orchids of the vandaceous alliance, to lose older leaves. This likely is the result of the plant putting energy into new growth at the expense of the old growth. There may be precipitating factors, however, such as a period of cooler temperatures and/or reduced light levels.  I notice that this happens more on my older plants than on the younger vandas/ ascocendas.  I would be more concerned if this starts to happen on the newer leaves.