We got Feathers II a little over a week and a half ago and for most of this time I thought the dark ends on his fins/tail were part of his coloring because his body is very dark as well and it didn't seem to be changing at all. When I compared the way he looks today to a pic of the way he looked the day we brought him home, though, I do think that maybe the dark part is slowly progressing and his bottom fin (sorry, I don't know the actual name for it) is looking a bit tattered.
I'm preparing water for a 100% water change with AQ salt and stress coat but meanwhile I wanted to get some other opinions because I'm sort of a new fish owner and don't really have much experience.
Please let me know if you think the first pic looks like a case of fin rot to you. The second pic is how he looked the day we got him - as you can see, it hasn't changed a whole lot but his bottom fit looks worse to me now than it did then. Further complicating matters is the fact that until a few days ago he had a plastic plant (which you can see in the 2nd pic) on which he could have torn his fin; that has since been replaced with the silk plant in the first photo. Sorry the pics are not of great quality and are huge; I am doing this on my phone.
BTW, I already realize his home is too small for him; I've ordered a bigger home and am waiting for it to arrive and meanwhile am doing frequent water changes (2x/wk)
I don't want to treat unnecessarily, but I also don't want to fail to treat either!