Wait and see if the (previously shaded?) leaves soon turn purple.

Or look to see if they are all on specific shoots coming from below the purple top, indicating they are rootstock sprouts that need to be cut out.

I have not encountered purple smoke bush being grafted before, but maybe that has sometimes been done.

Or maybe you have a reversion to green occurring, again not familiar to me but perhaps sometimes seen.

Others posting here in the past have been hot on cutting the whole bush down low on an annual or otherwise frequent basis, to be grown as a foliage plant. I am not impressed by results of this treatment seen in my climate, the replacement shoots writhing about like Medusa's hair on her severed head, looking for the rest of the body.

And you get no cloud of "smoke" if you stool it.