Often not eating can relate to internal parasites. So treating with a dewormer might be a better option initially.
Hikaro Prazipro has Praziquantel.
Fenbendozole comes in a liquid form as a Liquid Goat dewormer. It is absorbed through the fishes body. Very good results.
edit: metronidazole has been the most recent popular effective dewormer. Personally I have always had very good results with the fenbendozole flakes and liquid goat dewormer.
In the future, you can purchase fish food (Angels Plus has an assortment with different meds for any time you get a new fish).
The blind fish could stay while the sick fish is treated. It is used as a preventative measure frequently and when I had Angelfish I would treat them upon arrival and about every 6 months.
New to FW fish? First tank in a long time or EVER??? Need some info on keeping fish?
Start here - Aquarium Advice Article
FW Favorites right now Clown Loaches, any shrimp - SW Vase Red Mangroves