Box Woods turning yellow and die
There are a few things that seem to be shown in your photos. The shrubs may be planted too deeply- how long have they been in the ground? If they were just planted within a year you may be able to re-plant them so they are not too deep, making sure the root flare is at ground level and not covered with soil or mulch. Here is planting info should you need it( planting a shrub is he same as a tree) - https://extension.unh.edu/resources/files/resource000491_rep513.pdf
The light tan to whitish leaves look like winter burn. This usually happens because the wind and sun over winter killed these leaves, and the shrubs were not well watered before the ground froze in the fall. Evergreen trees and shrubs must be watered in fall up to a hard freeze- usually sometime in November around here- unless we have a rainy fall. A burlap screen on the south and west sides of the shrubs can help protect the shrubs in winter from winter burn.
There are some leaves with a rusty color - this can be from insect damage, like spider mites or leaf miners. Examination of some leaf samples at MSU Oakland county Extension office will help determine if they are present. Take freshly clipped samples in (showing damaged leaves and green leaves on the same branch) and for a small fee they will look at them. Call on Monday or Tuesday to determine when someone is available to look at samples for you. 248-858-0902
Alternatively you can send pictures and samples to MSU Plant Diagnostic.lab,
Website has a fee schedule and mailing instructions.
A serious disease, boxwood blight, has been found in Michigan. If your shrubs have this disease they need to be removed and disposed of properly. There is no cure for this disease and it can spread to healthy boxwoods in the neighborhood. The MSU Lab can confirm whether blight is the issue or not. Here are some pictures and detailed info-
Treatment of insects can be done but spider mites are treated differently than leaf miners. The Extension office, or the lab, can give you treatment options.
Here is info on both, should you need it-
I hope this just turns out to be some winter kill, and that can be cared for by watering and pruning out the dead branches. Thanks for using our service.