I just lost my nobile dendrobium that I'd had just over a year, but I had previously taken some of the new growths off and put them into their own pots, and they look to be doing fine, so I'd like to try to figure out what caused the parent orchid to go so that I can hopefully prevent it from happening to the babies.

So here's what happened:
It has been almost a year since the orchid lost its original flowers and leaves, but the original spikes were still green, solid and healthy, and it had been putting out new growths for about 6 months, so I figured it was doing alright. Then about 2 weeks ago I noticed that the original canes were turning yellow, and some of the newest growths were losing their leaves. I figured this was because I had gotten busy lately and let it dry out for too long, so I watered and waited.

Then one week ago I noticed that the yellow canes were starting to get mushy, so I unpotted the orchid, figuring I'd find massive root rot, but the roots were AMAZINGLY healthy--lots of branching, tons of white growing tips, and no mushiness anywhere that I could see. So I cut off the mushy older canes with an exacto knife, applied cinamon to the cuts, and then repotted what was left (about 4 thin, newer canes). Today I discovered that the remaining leaves all fell off, and that the thin canes were mushy at their bases (where they branch off from each other).

So sadly, I did not catch this orchid in time, but as I said before, I'm hoping I can still keep the babies from this plant alive. So has anyone experienced this sort of thing before, and know what I might be up against, and how to keep it from spreading?

Also, not sure if it's related, but I recently had a very similar thing happen to a spider plant baby that I got from my mom 3 months ago (it's leaves turned yellow and rotted at the base, but below the soil the roots looked plump and healthy)--are there any plant diseases that can affect both spider plants and a nobile dendrobium?

So that may not be much to go on, but if you have any ideas, please let me know!