I suspect it is the effects of autumn and is natural. Have you had a mild frost or sudden drop in temperature? is it the first time you have seen this happen?

welcome to GoY too.

Thank you, I'm hoping it's natural, there hasn't been anything unusual with the weather and it's not happened in the 5 years since planting.

Kind regards

Some of of the leaves on a few ccv i have also turned pink recently, dont think this is unusual, probably due
to temp drop / time of year.