Prune off all browned branches, since they are dead or too weakened to replace lost growth. They don't appear to be limited to winterburn, which has affected many evergreen plants this year (when winter weather conditions caused some leaf tissue drying/death and browning). The cause is hard to determine from the visible symptoms, and there may be overlapping issues causing dieback in one plant versus another, even though the symptoms look essentially the same.

One possibility is Botryosphaeria canker, an opportunistic fungus that infects stressed and injured plants, often during periods of drought. Most of Maryland has been in a drought for the better part of two years, and canker dieback can be one consequence of that, even if the rest of the plant looks fine. If you haven't been already, you can monitor the plants for watering needs to alleviate any ongoing stress. (Especially for the Pieris in the last photo, which doesn't always take well to growing in home foundation beds due to soil compaction and pH issues.)

The Japanese Holly in the first photo might be dealing with Thielaviopsis, a particular type of root rot, if the soil isn't acidic enough, is over-fertilized, or has stayed too wet at some point (there are other stress risk factors, but those are among the most common for that disease). As with Botryosphaeria dieback, all that can be done is to prune out the damage.

The Chinese holly (second photo) has both weather- or canker-related dieback and potentially a scale insect pest problem. The black residue on the leaves is sooty mold, a fungus that doesn't infect plants but which grows on top of honeydew, a sugar-water type of secretion produced by sap-feeding insects. In this case, the most likely insect culprit is a type of scale; usually we see Cottony Camellia Scale on hollies (despite the name of the scale, they feed on a variety of unrelated plants). You can learn more about this scale and the mold on the linked pages. Scale management, when needed, can be challenging due to the dense growth of pruned holly shrubs, and often involves the use of one or more insecticides. The sooty mold will weather off on its own, but if this drought continues and rains are too light or infrequent, it won't wear off as quickly. Sometimes certain horticultural oil insecticide products are also labeled for the suppression of sooty mold, and might speed-up its disappearance. If used, be sure to follow all product label directions.

Miri