Dendrobium in trouble

I have had this Dendrobium phalaenopsis NOID for about a year. It did well through the winter, putting out a new growth. Recently though, it has been dropping leaves. It has lost all of the leaves from the new growth, and a few others from the rest of the plant. I took it out of the pot, and a lot of the roots are soft. The media it was in looked fairly broken down. The canes themselves are still hard. Any advice would be very appreciated.

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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

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.

What temperature range is it exposed to?

During the summer, probably 75-85 at the window.

Dends do tend to shed leaves, but it probably needs to be repotted if you think the media is broken down. Remove any completely dead roots and clean the plant up a bit (remove the papery sheaths, etc) and repot, then keep it in a low-light area for about 5 days while it recooperates.

Do you let the dend dry out before you water? Sometimes plants leaves will turn yellow and drop if you are overwatering...just a thought.

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How about in winter?

In the winter, it was about 70 in the sun and probably 60 at night. Well, I got it repotted into fresh mix and a 4" clay pot. It was probably being overwatered, due to the condition of the media it was in. There were some very broken down coconut husk pieces in the middle of the pot. Hopefully now it will drain better and put out some new roots. I peeled away some of the papery sheaths, and there is no sign of insect or fungal damage, just bright green canes. Should I fertilize the plant right away or just use plain water?