If you want to try antibiotics, Baytril is what you should use. You can get it over the counter here:
Baytril 10% - All Bird Products
Enrofloxyn: Bird Medications - Ladygouldianfinch
https://www.ladygouldianfinch.com/product_baytril.php
The dose I would use is 0.07 ml per pound of body weight orally twice a day for 3-5 days.
Unfortunately, it's banned for use in poultry, but many people, myself included, still use it.
Baytril 10% - All Bird Products
Enrofloxyn: Bird Medications - Ladygouldianfinch
https://www.ladygouldianfinch.com/product_baytril.php
The dose I would use is 0.07 ml per pound of body weight orally twice a day for 3-5 days.
Unfortunately, it's banned for use in poultry, but many people, myself included, still use it.