Can you tell us more about the plants? When were they planted? Has anything been sprayed on or near them? When did the symptoms first start to appear? Look closely at the new stems to see if there are any black lesions that look like a Sharpie marker line drawn on the stem. Also, keep an eye on the plants and see if there is any defoliation. Those would be signs of boxwood blight, which is more common in new plantings of boxwoods compared to established plantings. https://extension.umd.edu/hgic/invasives/boxwood-blight
If there is no sign of the stem lesions and leaf loss, it would be something else. It would be helpful to know when and how the boxwoods were planted and maintained.