Certified GKH Gardening Expert
You may want to try watering more deeply. If you water frequently but only for a short period of time, the water may only be sitting on the surface without getting too deep, which means that it will evaporate quickly from the soil. Less frequent but deeper watering will help your shrubs more because the water stays longer.
You may also want treat the plants with a fungicide. The browning could be caused by a fungus. There are several that could cause this, but a general fungicide will treat most of them.