I think it is hard to kill polemonium because the plain one I have in my large bed dies back as the weather gets hot. The leaves just yellow and die. Sometimes there are no leaves left but next spring it grows and blooms. I'd wait til bloom is over and trim it back by half then see what happens.

I have one Stairway to Heaven in a shadier area which doesn't die back. It has been a great plant with interesting foliage.