Brian, I doubt that the high humidity in your greenhouse has anything to do with your tree problem. Humidity in my greenhouse, especially during the winter months sometimes causes "rain" to fall from the glazing. On warmish days I turn on the exhaust fans to reduce the humidity. However, over the 30 years I've had the greenhouse, I have never had a problem. In Florida during the summer many days the humidity is 100 percent. On Okinawa, when I was in the Navy, the humidity was near 100 percent the entire summer, no problem with the citrus.