What I might do in this situation if I wanted to keep the plant, is dig it up, wash up the roots and try growing it in some new potting soil in another part of the yard, out of direct sun and see if it can support the new growth then. When my plants are unable to support new growth, I often find rotten roots.

Loretta, it occurred to me last night that I'd moved a bird feeder closer to the Calycanthus. Do you think the sunflower seed hulls might be affecting it?

Because they say sunflowers are allelopathic? I couldn't really answer that just from my experience.
Do you have a lot of hulls around this plant? It is worth to remove them and move the bird feeder or use hulled seeds. That would be interesting if that worked.

Yesterday, I dug it up and moved it to a spot about 30' away - which in fact is better visually 'cause I can now see it from the kitchen window. There was lots of new growth coming on it. There was, of course, the requisite 50 lb. boulder about 5" down in the spot I where I wanted to plant the shrub, but after quite a bit of wrestling I got it out and added an entire bag of humus to the hole, mixed in the native soil and planted. The root system looked good and healthy - so now I'll just have to wait and see.

Thanks for your suggestions, Lorretta.