Jade plant rotting from inside out
My large jade plant is rotting from the inside out. I noticed that leaves were dropping off and some were discolored. I thought that it might have mites so I used a commercial brand to kill them. The plant had this a couple years ago and it worked then.
Then i noticed about 3-4 days later one of the large branches looked like it was pinched. I touched it and it fell off. Upon inspection the inside was hollow and black but the outside of the limb looked normal.
I have had the plant in a low light area out of necessity for about a month prior to this happening and was watering the plant weekly. I put the plant outside about 4 days ago and a couple days later I noticed another branch did the same thing.
I saw that somebody had a similar problem about a year ago but there was not a solution posted.
Anybody have any ideas. This plant had been in the family about 20 years and I don't want to loose it.