Voltuella Blight / Macrophoma?
It is hard to tell if the browning is old volutella or just winter injury. The plant looks pretty good overall, especially for this time of year. They will soon flush out new leaves.
The biggest thing to be worried about, especially if this is a new planting, is Boxwood Blight, which would be expressed with defoliation and other symptoms. Problems of Boxwood, including Blight, are covered here: http://extension.umd.edu/hgic/boxwood-culture-and-diseases-including-boxwood-blight
The other issues are secondary. Prune out any damaged/dead leaves and branches on a dry day. Selective thinning will help to keep them healthy.