We have seen many arborvitae dying off this autumn from the stressful summer they experienced -- high heat and drought -- and unfortunately browned branches/foliage will not recover. Were the plants monitored for watering needs during the summer drought? (Several areas of Maryland, including much of Prince George's County, are still in drought, which has not abated much for almost the entire summer.) While over-watering and under-watering can cause similar dieback symptoms, the pictured damage appears to be from insufficient water. Even if the other plants are still green and looking good, make sure they're getting the water they need by feeling the soil periodically. If somewhat dry to the touch about six inches deep, water the root zone thoroughly. In evergreens and many trees, dieback can appear some time after the damage has been done by stress, when intervention would be too late to save the plant.

The final photo, where only some of the inner needle clusters are yellowing, looks normal. Evergreens do keep their leaves in winter, but it is natural for all of them to still shed some old leaves each year, either in autumn or spring. If the outer foliage on that plant looks green and only some of the inner foliage is yellowing and shedding, that isn't necessarily an indication of a problem, though to avoid it becoming worse due to stress, also keep an eye on watering for that plant so it doesn't stay too dry for too long.

Miri