Tapien Verbena fading

Hi,
I have used the Tapien Verbena for quite some time and usually its a great performer but the last 2 years it seems to struggle. As I recall I bought these plants several years ago, perhaps even 5 years ago but they spread and re-root if the surface soil is moist. I'm zone 8-9 and they are in full sun.

I suspect these behave somewhat like annuals in that after a few years they burn out unless there is a lot of rerooting. I did try moving some newly rooted stems to a bare area but they don't do much either.

The pink Verbena combined with lavender is a spectacular combination, the colors remind me of a Monet painting. Is it possible that these have a limited life? I'll try some new ones, they are only available at the independent nurseries.

Thanks