You are welcome to share more photos if needed; you can reply to the same question thread in order to attach a set of three different images, and can reply multiple times if necessary to send them all in. (Or, you can paste them into the body of your reply...either approach works as long as image files are at least 1MB in size each so we can zoom-in.)

From what we can see, although some of the symptoms are not in focus (image "cultivar 1b," if you wanted to retake that picture), the prevailing symptom appears to be due to Boxwood Leafminer, a very common insect pest specific to boxwoods. The faint yellow leaf spotting is probably from this year's generation, which has paused development during the high heat of summer, and any larger and more orange-yellow spots, leaf blistering/puckering, and leaf backs with holes in them would be from prior generations. (There is only one generation per year. Management information can be found on the linked page above.)

Some cultivars have more inherent resistance to leafminer than others, though many of the dozens of boxwood cultivars on the market which aren't fairly new varieties do have some vulnerability. Most modern boxwood cultivar breeding has focused on improving resistance to fungal Boxwood Blight (which we do not see indications of in your photos), though some also improved leafminer resistance, since they can be one of boxwood's most damaging pests.

Some of the leaf browning and drying might be due to environmental stress or a relatively minor infection like Macrophoma Leaf Spot, also addressed on the page above. Trimming to remove dead stem tips and to improve air circulation within a dense plant can help to reduce the risk of re-infection. Trimming can also remove most leafminer larvae without needing to resort to pesticides, which tends to be the only other recourse since the larvae are inside the leaf layers and shielded from contact-type insecticides. Leafminer infestation can contribute to premature leaf drop of the older foliage.

To reduce any stress on the plants, make sure they're being monitored for watering needs during this ongoing drought. Boxwoods have fairly shallow roots for a shrub, and are not very drought-tolerant, though they don't want to be kept wet either. They also don't fare well if mulched heavily to try to counteract soil heating and moisture loss. (Mulch atop boxwood roots should ideally be limited to only about an inch of depth.)

Miri

Thank you for the additional photos; they do seem to indicate leafminer presence, and possibly also Macrophoma (the latter would be hard to confirm from photos, especially if dead leaves are not producing spores at the moment because it's so dry). If you peel apart the upper and lower leaf surfaces on some of the blistered-looking green leaves, that should reveal the yellow or yellow-orange leafminer larvae.

Miri