Who Gives A Fish Forums

I'm dealing with a pretty tough situation with my female tankmate, sushi. I've never had this issue with my boys before, so I'm kinda in uncharted territory here. She's still swimming around and eating, but something's off - she's still the queen of the tank, but I can tell she's struggling. I don't want to keep her suffering if I can help it, that just seems cruel. I need some advice on what steps I can take next to try and help her out, and if worst comes to worst, I want to know the most humane way to let her go.

To better understand what's going on with your girl sushi, could you provide a more detailed description of the picture you posted? Specifically, I'm trying to get a clearer view of the growth under her belly region. Are there any red lines or markings visible? Is the growth protruding from her vent area? And how long has this been going on for - has it been a recent development or has it been present for a while now?