1 of my Odessa barbs has had dropsy twice recently. The first time was in July. I noticed it a bit late but managed to get him into a tank with epson salt. This last week the same fish got dropsy again, but I caught it a lot sooner so he's doing fine again. I'm confused as to why he keeps having this problem. None of my other fish have been sick since this started and I've not noticed him getting picked on. Anyone have an idea as to why this is happening?