Jane, can you take a photo and upload it here so that folks can actually get a view of what's going on with the plant? I'm not real familiar with
Rose Campion (Silene coronaria) From what I've read it is a short-lived Perennial or Biennial plant but they readily reseed. Have you perhaps had a lot of rain lately which could be causing the roots to retain too much moisture? They like moist soil but not soggy so the issue could be water related. Hopefully someone who grows that pretty plant will pop in with advice.
~ By the way ... I love the kitty in your avatar photo, such a cutie!
