Ajuga withering . .

A few of my ajugas are withering up, where as others growing right beside them are thriving. I haven't seen any bugs or mildew. Ideas on what it could be?

 

I'd dig them out and check the roots for pests/root rot.

Ian

 

thank you, I'll check that out later this evening. It is 35 degrees at 7PM. The garden is in the west, so right after sunset I'll go look