Experts and BHG readers answer.
Boxwoods are dying
Make sure when you're watering that you are watering deeply. For well-established plants like your boxwoods, you might consider setting the hose on a trickle the size of your pinky and letting it run at the base of each shrub for 30-60 minutes. (You want the water to soak in deeply, not run off.) If they're not already mulched, mulch them with a 3-4-inch layer of organic mulch like shredded cypress or cedar. Finally, cut off a small branch showing the yellowing symptoms and take it to a Certified Nursery Professional at your local garden center for diagnosis. It sounds like the problem is just drought stress, but it could be that a pest has moved in and attacked your stressed plants, which is very common. With such a prolonged period of dry weather, it's doubtful that a fungus is your problem unless you've been watering from overhead and getting the foliage wet. It's more likely that an insect pest (possibly spider mites because they thrive in hot, dry conditions) has moved in. Plants that are stressed are more vulnerable and less resistant to insect damage.