I have a group of 6 SDs in my 150 as dithers for my JDs. When I got them they looked like typical silver, silver dollars lol. Since I got them about 6 weeks ago they have developed faint spotting and orange anal fins. They also get a black smudge on their sides that come and go. Has anyone experienced this before? I know there are many different types of SDs so I'm not sure what these guys are. I got them from petsmart for $1 a piece.