Matt, I have suggestion that may work. From what you have mentioned above, I have concluded that the main issue is humidity. This orchid isn't really difficult to grow. I have this plant growing under the following conditions, 60% shade, misted three times daily and rarely ever fertilized (do to time constraints). I try to avoid using pesticide and fungicide. The medium I have it grown in is coconut husk and charcoal. What I suggest you can do is to try growing it in sphagnum again but this time, grow the orchid in a humid location, example the bathroom.