I just got back after a 2 week holiday to find that my beautiful female guppy has what seems like a giant tumor on her side. I know it wasnt there when I left and the fish sitter didnt tell me that anything was wrong in her daily updates. I'm really worried here. I've isolated her in the hospital tank and she still seems perky and alert but I dont wanna risk my other fish. Should I let nature take its course so humanely euthanise her?