Years ago I planted a small Smoke Bush just past the drip line of a very, very old & large Black Walnut. There was no growth at all during the summer - stayed the same size & shape - and by the next spring it was dead. Don't remember if it showed the typical 'Walnut Wilt' & yellowing. (I was a juglone newbie in those days.)
Anyways, I don't know why it died - I've killed so many plants over the years, most of which were 'juglone tolerant'- but in this case Walnut trees were nearby.

Here is a page with a list of tolerant plants:

Here is a link that might be useful: Tolerant of Black Walnut

This may be too late for you, but I'll go ahead and mention my experience, in case someone else is trying to figure out what to do. Early this summer, I planted two smokebushes about thirty feet away from a black walnut in my yard - maybe ten feet beyond the canopy. They've both failed to thrive. The leaves turned brown in patches (and the purple one lost its purple color entirely), and a couple of branches have died off completely. It sounds very much like what happened to artdeco.

They might have just had a rough time getting established, but I think it's more than that. I went on the web to see what I could find about smokebushes - with some suspicion that the walnut was causing the problem - but there's very little information. Tentatively, I'm going to say that this is a bad combination, continus seems to be sensitive to juglone. (Just as a note: at the same distance to the walnut, there were already a fig, a magnolia, and even a lilac - all seem to be doing just fine.)

I'm going to try again with another smokebush in another location, to see if I can kill that one off as well.