Dendrobium in trouble

[JoeW]

Good afternoon! Great pictures. I don't know, but I am sure others will. A few questions to help with the diagnosis. Did the flowers bloom on a stem from the top of the cane or from all along the length of the cane? Rub the underside of the leaves with a white paper towel. Do you see rust or red? How much/what kind of light is the plant receiving? How often do you water and how dry do you let the plant get? Do you fertilize and if so how often and with what? Have you ever repotted the plant?

The older canes on my noid den. phals' shed their leaves. I have old canes with only one leaf at the tip. However, I am concerned to hear the new cane has lost it's leaves too. Joe

[Laura81]

The plant normally sits about a foot from a south-facing window. I have been watering maybe every 7-10 days since the growth matured with plain water. Before that, it was getting 1/4 strength 20-20-20 fertilizer once a week. I have never repotted it, but I can tell from the way the media looked that it needed it. The flowers came from the top of the cane- I know it isn't a nobile type. I don't think there is any insect damage- no strange spots on the leaves or anything like that. They just yellow one at a time and fall off. Does that second photo look like a fungal infection? There are some weird dark spots on that cane.