Established Korean box turning copper color on top
This does not look like a disease or insect issue. This looks like winter color on the boxwood. Stressors such as cold dry weather and a lack of moisture can cause some dessication. It is located against brick in a sunny area and this can be a factor. Sometimes this injury can be scattered. Maintain adequate soil moisture in the fall to prevent winter desiccation.
At this point we do not recommend a control. Monitor the shrub during the growing season and you may have to do some pruning eventually.