I currently have 1 common goldfish (6 inches), 1 comet (3 inches) and 1 london shubunkin (3 inches) along with a common pl*co in my 35 gallon tank. They have all lived there happily for the past 4 years without suffering from any type of illness. Ammonia levels are zero, and frequent water changes are done on a regular basis. Today while observing my fish, I noticed that my common goldfish had a small red discolouration on (her?) cheek. It is a circular in shape and is light red in colour. No other discolourations can be found on the body of the fish and it shows no other sign of illness. Is this something I should be worried about? Or is it nothing more than normal colour deviation that I should not concern myself with? Thanks for any help!