Golden Smoke bush

This bush leafs out in sections. Over a week between the first photo below and today. Also entire sections are dead. The leafing out over time is not new ‘behaviour ‘. Once the foliage is fully out, apart from differences in leaf sizes, the leaves look healthy. No spots. I noticed about a year after planting that the pruned stems had some dark spots between the bark and stem. The nursery guy said not to worry. I thought verticillium wilt as l have had that on a Japanese maple ( not planted in that spot) but the smoke bush looks healthy once it’s in full leaf.
lm thinking the plant is stressed… ? If it is diseased and l take it out before it is fully dead , what can l do to the soil so l don’t kill another tree in that spot. I’d like another smoke bush.

 

Smoke Tree (Cotinus coggygria)-Verticillium Wilt | Pacific Northwest Pest Management Handbooks (pnwhandbooks.org)

 

Reading this article, the only symptom my plant has is the spots on the inside of the stem. no die off, leaves are perfect once they come out and it has been this way for 5-6 years.. maybe more. ....so am I missing something? good to know how to clean up the soils as that technique probably works for many diseases.