Popeye is a serious case of gram-negative bacteria infection usually due to dirty water. U may need antibiotics to treat your fish & u have to do it fast!
Broad spectrum antibiotics include Maracyn - Two (Mardel), tetracycline (recommended), trisulfa (only effective when mixed with food), neomycin (SeaChem's Neoplex), nitrofurantoin (SeaChem's Focus) etc. In cases where food is refused, consider Kanamycin (SeaChem's KanaPlex) as it's absorbed by fish. Tetracycline is more effective when the pH of your water is < 7 as it tends to bind with calcium & magnesium, increase dosage if pH > 7.
Do not increase your water temperature. Good luck.