I planted a mixture of heath (Erica darlyensis) and heather (Calluna vulgaris) along the edge of my garden about 5 years ago- Zone 5b-6 (MA), partial sun. I have had mixed results year to year.

Parts of it look gorgeous, all green with red and purple flowers.

Other parts look dead....just twigs (usually, unfortunately, in the center of the plants....the new life emerges along the edges).

Should I radically cut the dead-looking branches to the ground?
Or will they eventually leaf out and bloom like hydrangeas do? (I'm not sure if they leaf out on old growth or not).
Is there anything I can do to improve their health?
To paraphrase Roseanne Roseannadanna, do I ask a lot of questions for a guy from New England?