I planted 4 Hebe shrubs about a year ago and they appeared to be doing great. However, A few months ago one of them started turning brown and losing foliage. I tried trimming off the damaged branches, waited a week then I sprayed all the plants in the area with a neem oil solution in the early evening in case it was a pest or fungal issue. I also applied a light fertilizer application in the event they were not getting enough nourishment. They are on a drip irrigation system and I was concerned that this plant was not getting enough water so I added another bubbler in its area. None of this helped and the plant died. Now the surrounding plants are showing signs of the same disease. Does anyone know what the disease is or how I can stop it? - Thanks in advance