Help identifying disease

[the_greg]

I have a three-month-old south American cichlid tank. Water parameters:

• pH 7.5
• Nitrates <20
• Hardness 
• Nitrite 0
• Ammonia 0
• KH/Buffer
• Water Temperature 80 degrees

I was away for a few days and returned to one sick fish in the tank. Does anyone know what this is?

[Colu]

Could be an injury caused by fighting I would add some aquarium salt 1 table spoon for 3 gallons and monitor for the next couple days if it's start to get worse then I would consider doing a course of kanaplex or maracyn2