My judii vibernum, probably 5 years old and always healthy and so fragrant has turned completely black. No dry or crispy leaves and no wilt or signs of stress, but it’s black. It started with a few branches and now the entire plant is black. Gets morning sun, good drainage. No signs of pests. Any idea of what’s happened and if I can save it? Should I cut it back? It’s big and in a prominent place. Thanks.