Not what I was talking about really, but it might work. Since you are in Australia, I'm not sure...I can't tell what the ingredients are in that stuff you have pictured. You would need to figure out the right dosage for the chick. You might want to just try calling the vet...sometimes they...
Might be a sinus infection. Treat the eye with Triple Antibiotic ointment (the kind with no pain reliever in it). Wash the eye first with human saline eye wash, then apply the ointment.. Do it twice a day. And then start the chick on antibiotics..water soluble is easiest, Oxytet might still...