Boxwood
This could be a form of canker. It will cause new growth to be an unhealthy-looking light green color and, as it progresses, the leaves and entire branches turn a light brown. The bark at the base of the branch is loose and will peel off readily. Any branches that look this way should be removed immediately, disposed of away from the plant and all leaves raked up. This disease can be easily transmitted, and all your boxwoods can be affected. They should all be treated with a fungicide. This treatment also will control most forms of blight.
With leaf spots, the leaves are straw yellow with small black dots, but it can be controlled by shaking out all dead leaves and destroying them and spraying with a fungicide before growth starts in spring.
Root rot (Phytophthora) causes clumps of pale foliage, sudden wilting and very quick death of entire sections or the whole plant. Infected plants will die, and the soil must be removed or sterilized (with steam). All soil infected with this problem can cause death for new boxwoods.
Keeping your soil light and airy can help prevent root rot. Fungus problems need to be treated quickly, and all dead leaves should be removed from around your boxwoods. Keep the plants neat and make sure the soil is not waterlogged, and you can avoid most fungus problems.