Ragged edges are generally a sign of tail rot. You definitely want to get it treated before it reaches the body, because then it becomes much harder to treat and is a definite threat to your buddy's life. I've used JFC with some success and am actually using it now since I noticed both my guys have some tail issues. Keep monitoring it and treat as quickly as possible because it progresses pretty quickly. A total water change and tank sanitation is probably also a good idea, because it'll make it easier to treat the fish without also having the bacteria living in the water working against you.