Geekboy, you are doing a terrific job fighting this. Keep up the good work. I had an extremely sick Brochis that recovered from severe septicemia so I have high hopes for your beautiful fish. We're all pulling for you and your goldies.
My older comet has been somewhat sickly in the past year, with a rather marked color change (she had quite a bit of orange before), and floatation problems. I've wondered it the yellowish cast around the head and fins was healthy. It wouldn't surprise me if there are pre-existing kidney problems, and some of these antibiotics are bound to be difficult to process. Your warning is appreciated -- I guess I can only wait and see.My too smaller ones managed to fight it off quickly with some meds but my large white comet was hit hard. I nursed her through the septicemia but dropsy killed her six months later. The bacterial infection caused kidney damage and they slowly failed. It took her 5 months of slowly swelling before the kidneys shut down completely. I had had her for 8 years at that point.
Hopefully you don't run into the same thing that I did and they go on a live for many more years. But just in case you lose one later this year you'll understand why.