Please help my female betta is getting worse

[Mmcaulif]

My Betta fish has popeye and has been lethargic for days. She spends half her time on her side and all around her mouth has turned whitish. I had her on Bettafix, and now she has completed 4 days of erythromycin. Today the popeye became 100% worse. She also hasn't eaten in 6 days. Her water parameters were perfect according to Petsmart. I originally thought that she had swim bladder because she visibly looked like her stomach was engorged and had became lethargic and was not eating. Within a couple days she went to the bathroom at least twice. She was in a community tank with several tetras, but I moved her to a quarantine tank with fresh clean water. I have 1 other betta that I noticed fin rot on, and she seems to be feeling and looking better after the erythromycin treatment. However, Blue just seems worse. Her popeye apparently wasn't that bad before because when I woke up this morning it was huge.

Please help

 

[KatyLLL]

Do you know how to euthanize? I had to euthanize a Dwarf Gourami this morning. The other alternative was to allow him to be eaten alive by the other fish. A little fin rot or some Ich are survivable if caught early. Bloating, tumors, laying on the side on the bottom gasping, swim bladder issues, are often going to be fatal. If the fish is sick with an incurable disease, then it is time to put it out of its misery. I do it with warm water and clove oil. I have had to euthanize 3 fish this year. If you own fish, or want to own fish, you need to think of what to do if the worst happens. One fish I euthanized got caught in the rotators of a circulation pump. That kind of terrible thing actually happens.

 

[Mmcaulif]

Thank you so much for the reply. As hard as it is to hear, you are right. She is not doing any better. I do not have clove oil, but have seen it used to humanely euthanize on a youtubers page (Solid Gold Aquatics). I have 2 other aquariums with goldfish and should have it on hand, and be prepared for this kind of thing.

Thank you for the painful, yet neccessary, and caring advice.