Could they have got too wet Izzy? They are only short term at best.

Maybe you planted them too deeply, or are they being dripped on from the gutters etc?

Hmmm! I'm wondering about both of those scenarios...maybe planted too deeply AND had lots of water.... in the form of rain!.....on them!

How short-lived are they, MG? They are certainly 'rotten to the core', Volunteer. I just 'stuck' them in the pots with a host of other winter plants...everything else thriving but I won't repeat this planting plan next year! Thanks both!

My understanding is just a few months, Bamboo posted on a question about ornamental cabbage recently. Yet I am puzzled as normal cabbage and kale just keep on growing.

Not sure about ornamental kale, but certainly ornamental cabbages don't look good by December usually - not because they've stopped growing though, Moongrower, but because they're blown, on a long stem, without the firm round colourful centre, so from an aesthetic point of view, not something you want to look at.

Ah that makes sense...