Please help! Diamond, my biggest goldfish is always very active and friendly. A big (5 inch body length) begger who loves to eat from our fingers. She seems fine and is acting normal, but today I noticed a red patch near the base of her tail, on her side, that is a little smaller than a dime. It seems to be beneath the scales and the scales at the rear end of the patch are slightly raised. No other issues. We had recently neglected water changes because of being on vacation and then overwhelmed