Add course builders sand that you can find in the cement area of the big box store. See if that helps.
I had the incredible wilting caryopteris too, I just found it a new home, not in my garden! I'd like to try another, they are wonderful plants. GOOD LUCK!

GGG

Sounds like it might be too much water to me too. By the way, did you know how easy caryopteris is to propagate? Any bit that touches the ground will root very readily, so try pinning a branch down - once it has recovered, of course!

Well, I decided to dig it up and put it in a pot. I'm going to use good draining soil, and cut it back (no blooms - boo hoo!), and I figured I could try to propagate the cuttings. If the potted plant lives, I'll re-plant it in the fall. If not, hopefully I'll have some cuttings to replace it!
Thanks for the tips and well wishes,
Pam