boxwood dropping leaves
The boxwood looks like it is trying to establish its root system. Boxwoods in general have a shallow root system. Your watering schedule sounds excessive. It is not recommended to water daily.
You will have to check the soil moisture of newly planted shrubs about once a week for the first two growing seasons until the root system gets established. Soil that is moist or damp to the touch is fine. You may need to probe with a screwdriver. If the soil begins to dry out, water the plant deeply. Do this up until the ground freezes. Do not overwater.
Make sure mulch is no thicker than several inches and keep away from the base of the stems. http://extension.umd.edu/hgic/trees-and-shrubs/post-planting-care
- Brown spots on green leaves.
- Defoliation starts at bottom of the boxwood and is progressing upward.
- Black canker on stems.
Thank you for these additional photos. The black lesions on the stems are a key characteristic of boxwood blight. Unfortunately, there is no cure for it. You will have to remove the boxwoods and as much of the remaining leaves as you can. We do not recommend re-planting boxwoods in this same location. Sweet box and pachysandra plants are also hosts of this blight. If your plants were under a warranty from the nursery from which you purchased them, you can go back to them and see if it possible to get a refund. https://extension.umd.edu/hgic/topics/boxwood-blight