It sounds like a classic case of boxwood fungi due to overwatering or damp, wet weather.  The clue here is the yellow orange color which leads me to believe the fungal infection is a Volutella stem canker. Now is the time of year to remove the unhealthy boxwood as the fungus is hard to control even if you were willing to use a strong fungicide. I suggest you replace with Ilex or Japanese holly or Nandina or even yews. All three of these evergreens come in various sizes so you can get dwarf or more compact forms or taller and spreading forms. Try to change the sprinkler system so it does not spray the foliage of your new hedge. Keep growing, Marianne Binetti