red sore?

Question
I just got back from vacation, and one of my fish has what appears to be a raised lump on it's skin (not a tumor, more like an injury or start of bacterial issue, I am not sure), and it is turning reddish. I am very worried and want to treat, but not sure what is the safest way to go. I live in Arizona and havent yet found a vet for fishies if you know how to do that. But, I only had my babysitter feed fishies every four days. They did appear to have some issues though when I got back, with some fin streaking but it's pretty well cleared up with my partial water change after a feeding of Hikari pellets when I came home late Saturday. I am worried because for a moment two new fish were accidentally put in my big tank, and I dont know if my fishy is suffering ammonia or stress from my vacation, or got something in this time from the other fish who were rescues from a petstore. What can I do to make sure all fish are safe from anything, and to heal this girl, I love her to death. She is a cute calico oranda. I can give you more details also, and dont mind spending the money but I dont want to overmedicate. Thank you soooo much. For now she is separated in a hospital tank with salt while I try to figure out if this is bacterial, flukes, etc. It just started showing tonight.

Answer
Hi, i will need as much information about the sore, how big it is, is there any infection. Even a picture would be good. you can email your information to me on Jody_62@hotmail.com i will see what i can do. I am going into the city tomorrow and will be away for 4 days so if you can get me the information by the morning (Australian time) then i can look in some aquarium shops for you. You might also like to try and ask one or two of the other experts just in case i cant get back to you. You have done the right thing by separating him from the others. Get me that information and i will try my hardest to help you! Good Luck!