Hi, I have kept mainly warmer orchids and decided to try growing draculas and masdevillas recently. The orchid lost a few leaves due to stress but it is continuing to lose leaves. The leaves start as yellow splotches before turning completely yellow and falling off. It is continuing to flower even though it is dropping leaves. It is in a glass orchidarium with heavy misting of about a minute a day. The leaves dry out during the night and the temps are from 60 - 70f.
Thanks,
yashasange
Mistking
Looking for a misting system? Look no further. Automated misting systems from MistKing are used by multitude of plant enthusiasts and are perfect for Orchids. Systems feature run dry pumps, ZipDrip valve, adjustable black nozzles, per second control! Automatically mist one growing shelf or a greenhouse full of Orchids.
I have a Dracula venosa and the same happened. I stopped the leaf yellowing process by moving it closer to my basement window - temps under 63f , 24/7 and watering with rainwater. My humidity is only about 55. Air circulation is good.
Maybe yours needs to be repotted as another possibility?