Did you ever get an answer to your question? I'm no expert by any means, but what I can say is that in my area, the biggest discussion around boxwoods and there health the past season, was the prevalence of the boxwood moth (along with mites, wilt, etc) which seemed to emerge out of nowhere and decimate entire plants very quickly. Could this be something in your area? (You often see bits of webbing if it's the moth, along with actually hearing small "popping" sounds close by during the spring/summer season of insects plaguing the foliage.)

I don't know what the problem is, but it isn't Box Moth. I've suffered that and can no longer grow box. It doesn't turn the leaves orange. It entirely defoliates the bushes and usually kills them stone dead. It's become a major scourge over here and has destroyed vast swathes of Box hedging.

This is definitely not the moth. These plants have been looking like this for a year or so. No leaf loss. Just unhealthy looking leaves.

Maybe take a few leaves or a branch in a zip lock bag to a local CA nursery and ask. Please support the local nurseries.

Yes, I didn't really think it was the moth myself - as it didn't look anything like what I experienced personally myself on my large boxwood which was attacked by those things (but I've been addressing with BT and plan to do so even more this season). Hopefully, you will find an answer!

I second/third sending a sample to your local extension office. There is also a line of products called TopBuxus that includes a foliar feed and soil fertilizer. I've fought off several different boxwood issues over the years (volutella blight and leafminers among them) and feel regular application of these products in combination with other treatments has contributed to overall healthier plants.