It's winter. They need the layer of fat to keep warm. The feed sounds good as long as you're not adding much of the 16% protein feed. I like Bar Ale, but I'm biased since that feed is from my home town. ;)
Edit: I've also noticed that older quail have more fat.
I don't think it will hurt to try the antibiotics.
Three years old is old for a coturnix. Her age and being alone may be factors in her health condition, though it sounds like you're treating her quite well. Even if she doesn't use hiding places, it's good to have them available for her just...
That looks like the second eyelid. I would start with a saline solution rinse to keep it clean.
How old is she?
How many quail do you have?
What is their home like? Bedding? How much space? Hiding places?
Is she eating and drinking normally?
Does her poop look normal?
Oh, yeah, it is dangerous, isn't it? I have a loaf of sourdough cheese bread proofing in the oven right now. My friend and her daughter are coming over in a couple hours and we're all going to enjoy it.
It turns out that one of my tenants had guests, and they helped themselves to whatever was in the 'fridge and on the counter. They didn't put my ketchup back where it was, so I couldn't find it and they ate all of the bread I made. I don't mind them eating the bread. I've always said that if...