I have ab 30 japonica boxwoods in a hedge that are turning a lite to medium to brown color. They don't appear to be dieing as on close examination of the leaves they are still moist, fleshy and alive. The brown color is primary and is mixed with some dark green. The extreme edges of the leaves are yellow. From a distance the plants look completely dead and brown. The condition is spreading from plant to plant (about 22 plants currently effected). I am in Sunset zone 18 which can get as low as the low 20's high teens about 2-4 nights/year on average. We have had about 7 - 10 days of upper to mid 20's nights already this winter.
Is this a dormant phase of the plant or could something else be the cause.