Hard to say without more info, please fill this out to help us help you;
Tank size:50 gallon
pH:Ran out of testers
ammonia
nitrite
nitrate
kH
gH
tank temp:26 degrees Celcius
Fish Symptoms (include full description including lesion, color, location, fish behavior): Fish is acting as it usually does, I put up a picture of the sore.
Volume and Frequency of water changes:Water changes once a week, about a quarter of the tank, sometimes less.
Chemical Additives or Media in your tank: Sometimes I add stress reliever (if I'm adding fish)
Tank inhabitants:A community tank (2 angels, 3 small goldfish, 7 danios, 3 barbs, 4 tetras, 2 snails and a pleco)
Recent additions to your tank (living or decoration):none
Exposure to chemicals:Just the stress reliever
Digital photo (include if possible):