It sounds like there might be mycoplasma gallisepticum or MG with the swollen eye. The LA200 might treat that, and other antibiotics are Tylosin, doxycycline, Denagard available sometimes online for pigeons. MG is a chronic disease, and can come and go throughout life. The flock should be closed since most of your chickens may test positive. Here is some reading about MG:
https://extension.umd.edu/sites/ext… Mycoplasma gallisepticum (MG) Infecti….pdf

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