we have had this jade for about 3 years, it has had no problem until about the last two weeks. The large limbs are drooping down and falling off. I check the soil with a soil tester and only add a little water when it says dry. I am going to try to add two pictures so you can see what I am talking about. sorry about the sideways pictures, I will work on my posting abilities later.
To make sure you don't loose all the plant - cut off a couple of the healthy tops and re-root them. I can't tell for sure, but it looks like some of the stems between the root and the top are dieing and cutting off the flow of nutrients to the leaves.