We viewed your photos. This does not look like boxwood blight. https://extension.umd.edu/resource/boxwood-blight

We see some symptoms of volutella, a fungal disease  https://extension.umd.edu/resource/volutella-blight-disease-boxwood (diseased branches can be pruned out);  boxwood mites ( For light infestations, use a strong spray of water from a hose to dislodge the mites); and possible planthoppers (twig closeup photo) No control is necessary. https://extension.umd.edu/resource/planthoppers-flowers

These are normal problems on boxwood. 

Left photo - boxwood on left (off color and declining) looks like a possible root, cultural, or physical injury. Look around the base of the plant and the trunk for problems. 

Root issues - Check around the base of the plant to see if there are any physical injuries, signs of chewing, and vole tunnels. Voles (type of meadow mouse) are a big problem with boxwoods. They feed around the base of the plants and the roots. The mild winter we had was favorable for voles. Mulch should be thin no more than and inch or two and keep away from the base of the plants. Boxwoods are shallow rooted. https://extension.umd.edu/resource/voles 

Check the soil drainage. Boxwood require good drainage. Make sure there are no downspouts  dumping water in the root zones. If so, divert  to another area. 

If there has been any root disturbance or digging in the area, this can affect the roots. 

Brown Boxwood in the middle - we cannot tell if it is part of the boxwood on the right. Look around the base and trunk. Look for broken branches, physical injury, etc. 

No chemical controls are recommended. At this point, we recommend that you monitor for the above issues. At this point, we recommend that you prune out the dead/affected foliage when it is dry. Remove old fallen leaves and diseased leaves that have accumulated in the branch crotches.The boxwoods need to be thinned back into shape, not sheared. Thin the boxwoods to improve air circulation and light penetration. See the above link for a pruning video and how to manage and diagnose boxwood problems.

Also, if your boxwoods are located in full sun, they prefer some afternoon shade. They have a shallow root system so water during dry periods and make sure mulch is no thicker than an inch or two and away from the base of the plants. https://extension.umd.edu/resource/boxwood-diagnose-manage-and-prevent-common-problems

Marian