We have a wounded fish, it is one of our Silver Dollars. The marks on it are very strange, so much so that I took a photo of it and showed it to one of the staff at our local aquatic shop. The staff are all fish keepers and all very knowledgeable.
He said that the fish had either cut itself on something, Silver Dollars are very skittish or one of the other fish attacked it.
The fish will either survive or die, we really took the photos into the shop in case the staff took one look & said, 'Oh yes you've got lower Burmese gut rot' or something equally obscure that was going to infect the entire tank.