Fish can get tumors so it is possible that is the lesion in these fish. Fin and/or gill rot is also common in fish. This is a bacterial infection of the fin and gill. It can be secondary to trauma and is commonly associated with poor water quality. Severe damage can be surgically removed. Treatment includes antibiotics in food or water, injectable or topical antibiotics.
Consult a veterinarian who is comfortable with fish and exotics.
Consult a veterinarian who is comfortable with fish and exotics.