Sick Fish

[Fishlover08]

I have two goldfish that I brought four years ago when they were babies, and now they are almost as big as a baby koi fish. They are in a 54 gallon aquarium.
The larger one has a reddish/ pinkish things all over her....well not all over but on its on her....yes, I say it's a her, haha
and I went to the store and they gave me some powdery packets to treat bacteria on her, and I have to do that for three days in a row.... has anyone ever come across this who has goldfish?
Any advice would be greatly appreciated.

 

[Aiken Drum]

Could you post a photo of the fish and what is in the packet?