Hollow in the center, green all around the edge, like donuts? Or irregular patches of brown, that reach to the edge in places?

Thanks for responding, bboy.
Irregular patches of brown that reach to the edge in places.

Then some kind of damage, perhaps due to the winter we had. Dig it all up and try replanting the good parts only.

Plant is native to our area but is seen wild only at places like sandy flats near beaches.

Thanks bboy. The two hebes behind them are in bad shape as well. They made it through the really snowy winter two years ago. But perhaps not this last one.

Thrift is not tender but may have had a problem with the cold + damp this time. When I have seen it wild it has been mostly (always?) scattered little tufts in very coarse soil, where it was open and windy. It seems mats of it in more sheltered sites might be liable to collect too much debris over time or just become too soggy due to the presence of its own growth.

Rock gardeners and the zonal denial crowd know that planting in mounds or beds of coarse soil can keep plants going that would collapse in ordinary soil, on level ground.

I've had patches of thrift brown out over the years too. I just replant, it is cheap and such a cute little plant...