<<This can definitely be a symptom of an internal problem. Most likely the same as above. This one should also be isolated and please keep a close eye on your other fish as Septicemia is contagious.>> The common goldfish has white patches on the right side of its body which looked like fading color but then It turned into a missing scale it is not red or bleeding . <<I've had my own goldfish do this without anything being wrong with them but since your others are showing symptoms this definitely bears watching.>> I check all the ornaments but nothing with sharp edges are in the tank. One major thing that happened to my tank last year is I had a major PH crash and have not been able to control it since that happened. I have added ph correctors that did not seem to work. One day I noticed one of the ph correctors I bought was baking soda. I started adding baking soda to the water that's been working so I use it when I notice the PH is low.