Where are you located (state, USDA Zone?) I'm confused as to what they were planted in. Did your husband dig an oversized hole in the clay and fill in the space with potting soil? Was this a peat-vermiculite mix?

I think the roots got drowned, with the clay acting as a plastic pot. It would not matter what the filler was, unless there was some sort of drain hole at the bottom, as there could be in a raised bed or on a slope.

My Caradonna cycle through a green, bloom, brown, green basal foliage, bloom, etc... stage all summer.

When the top foliage looks ragged and brown, I cut the plant back to the green basal foliage, then it does it's bloom thing again. I get three bloom cycles off of the Caradonna, though the last two cycles don't produce as many blooms as the first. The cutting back at least keeps the foliage mounding and green.

Cameron

My experience has been the same as Cameron's. The foliage can get pretty ratty looking as the summer wears on, so I cut it back to the basal growth after it finishes blooming and fresh new green foliage ensues. BTW, I also treat S. 'May Night' the same way.