My dendr came from Home Depot. It was so Beautiful when I picked it out

Then about a month later I discovered the horrible mites. Well those are gone b-cuz of transplanting to new pot w/new bark and treatment w/insecticidal soap. Now it's sick with something else. The stems start to shrivle and dry up while the leaves get yellow then brown spots and fall off.

Other parts of the plant are doing great...it just got thru flowering too. I just tried some systemic treatment that I got for my roses. I figured either I'm gonna kill it,do something or nothing at all. Can anyone tell me what's going on??

I love the plant beause of when it flowers it just is beautiful but can this be treated?