Doxycycline and ciprofloxacin can treat symptoms of mycoplasma gallisepticum (MG.) But amoxicillin will not. I would keep checking the eye for bubbles or pus or a foreign body twice a day before applying the tobramycin drops. It can be hard to tell if the swollen eye is from a respiratory disease, or from pecking or getting debris into the eye.
The “one-eyed cold” that you mentioned, is probably MG, since usually one eye is affected from conjunctivitis and it can then affect the sinus. That can spread to the other eye. Chickens get viruses, bacterial, and fungal infections.
Here is some reading anout MG:
https://extension.umd.edu/sites/ext... Mycoplasma gallisepticum (MG) Infecti....pdf
https://thepoultrysite.com/disease-...tion-m-g-chronic-respiratory-disease-chickens
The “one-eyed cold” that you mentioned, is probably MG, since usually one eye is affected from conjunctivitis and it can then affect the sinus. That can spread to the other eye. Chickens get viruses, bacterial, and fungal infections.
Here is some reading anout MG:
https://extension.umd.edu/sites/ext... Mycoplasma gallisepticum (MG) Infecti....pdf
https://thepoultrysite.com/disease-...tion-m-g-chronic-respiratory-disease-chickens