Thank you for your question, Lori.  Your shrubs have a water mold described here:  https://pnwhandbooks.org/plantdisease/host-disease/boxwood-buxus-spp-phytophthora-root-crown-rot

This is a fungus-like problem, which happens when the soil has inadequate drainage, and the roots rot and die.  There is really no "cure" for this.  The only fungicide available to homeowners ("H") is Monterey Garden Phos, but it just prevents further stems and leaves from dying when applied according to label directions.  You can remove the already dead portions of the shrub; if the fungus doesn't return, some of the plant may grow to fill in the holes.  There's probably nothing you can do at this late date to prevent water from building up, but you should monitor how much the shrubs get, and not over water.  Good luck!