looks to me that this fish has a bad case of hex (HITH) its gut seems sunken in which is the sure tell sign for hex. Low energy and the wound is not getting better in clean water but seems to be spreading. Treat this fish as soon as you can with some antibiotics. And if it is eating soak its food in Epsom salt solution and feed it that way for 10 days to get rid of what parasites it may have. Keep the lights off as much as possible also. In the health and disease section there is a thread you can read that will give you detailed instructions on how to cure this fish. Good luck !
My gt has hex to the max he wont eat to save his life so I disolved some epson salt in some tank water got a syringeand forced .5 mls done his throat drastic times call for drsstic measures its either this or he dies.