It's hard to say, though if you can share a photo, we might be able to narrow-down the diagnosis. Leaf loss can be triggered by root stress or death, which in turn can occur with excessive soil dryness or wetness (poor drainage). Opportunistic fungal infections can set in when plants get too stressed, though some fungi take advantage of drought and high heat while others prefer wet weather. No fungicide cure is possible, but depending on the cause of leaf drop, the plant might recover and leaf-out normally in spring. Otherwise, it may need to be replaced.

Miri

Thank you for the photos. The symptoms of leaf drop and premature fall color appear to be due to abiotic stress; that is, caused by environmental conditions and not a living agent like a pest or disease. Typical sources of abiotic stress in summer include what you might expect: high heat (like what might be reflecting or radiating off of that wall, if it receives any direct sun) and drought. Were the shrubs being periodically watered prior to this week's rain? If not, then drought stress is the primary suspect, and leaf drop may abate after the recent rains. When monitoring for watering needs, feel the soil around six inches deep in the root zone and water thoroughly when it becomes somewhat dry to the touch at that depth.

Miri