It could be you are getting a late freeze and the buds are dying. Next Spring keep an eye on it and see if you see any buds. If you see buds and then you get a late frost you will be able to tell that it is the late freezes.
The soil might be to rich. They do not like rich soil. I had problems with a purple one when I had a service fertilizing and weed control for the lawn. They were spraying the bush area.
They need late afternoon sun especially.
