Peony Rotting

I have a peony Bowl of Beauty growing in my gardening. It has bloomed brilliantly each year but I've noticed that there are only three stems growing through this year and when I've tidied all the old dried dead stems away some of the main plant has come away and appears to be rotten. Is this plant suffering with some sort of virus and I need to dig out the plant or is removing the rotten parts of the plant enough to help it survive?