Chicken gets really sick, then goes blind??

[Kendal]

So I have a 2 year old Australorp hen. About 2 months ago she got really sick, she wouldn’t eat, drink, or walk at all. I considered culling her but I wanted to give her a chance to get better. After a week or so she started getting better but acted really weird. She’d just walk in circles, I still waited holding out hopes that she would get better. She finally started eating and drinking again, but I soon noticed that she was now completely blind. Fast forward to now and she’s completely adapted, she eats and drinks and lays eggs again. She’s back with the flock and no one else has gotten sick, they don’t even pick on her. She seems perfectly happy other than the fact that she bumps into stuff sometimes. But I noticed that before her eyes were a dark brown color and now they are gold, her beak has also turned almost all white. I just want to know what could have caused all of this? They free range, could she have gotten into something or gotten hurt somehow? Or is it a disease and she doesn’t need to be back with the rest of the chickens? Any ideas?

Before (her comb is a little pale here I think, she was sitting on eggs in the middle of summer and didn’t drink or eat much)

Now

 

[Svaness]

Is that bump on the side of her face normal? Possibly an abscess?

 

[Kendal]

She’s had it since I got her a year ago. I’ve never really messed with it, but it doesn’t seem to bother her. You can see it in the first picture too, just maybe not as well in the lighting. Could it be cancer or something?