Thank you Mark for your question to "Ask Extension".  Your boxwoods are definitely showing signs of phytophthora root and crown rot.  These are water molds, fungus-like microorganisms that cause root rot or crown rot.  For symptoms to show your plants have had significant root damage and will eventually die. If it's any consolation I am going through this same issue. The pathogen remains in the soil for a very long time and should not be replanted with susceptible plant for at least three years.                   Examples of resistant species suggested by extension agents in North Carolina include Nandina, Chinese holly (cultivars including 'Rotunda', 'Dwarf Burford' and 'Carissa'), liriope, Indian hawthorn, and Camellia sasanqua cultivars (Camellia japonica is highly susceptible). The rhododendron hybrids: ‘Caroline’, ‘Martha Isaacson’, ‘Professor Hugo de Vries’ and ‘Red Head’ are considered resistant. In addition, the azalea cultivars 'Formosa', 'Fred Cochran', 'Fakir' and 'Corrine Murrah' are considered highly resistant. Other resistant azalea cultivars include Rhododendron poukhanese, ‘Formosa’, ‘Fakir’, ‘Corrine Murrah’, 'Merlin', 'Hampton Beauty', 'Higasa', 'Pink Gumpo' and 'Delaware Valley'. Good drainage will also need to be provided to prevent this disease from returning.
    I hope that this information is helpful and as always Happy Gardening.

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