Some sad news here.
I had a pullet that several months back was wobbly on her feet. She was about 13 weeks at the time and when I inspected her I found a huge infection from a wound on the back of her neck. I gave her 2 shots of penicillin 3 days apart and she seemed to recover fine.
She's now 21 weeks old and a few weeks ago she started being wobbly on her feet again. I inspected her and found no injuries, but did find that she has no meat left on her - all you feel when you hold her is her keel bone and her crop. I knew it wasn't anything contagious, but couldn't figure out what it was. No symptoms other than wobbly on her feet and it didn't look like Mareks, didn't look like cocci, etc. I dosed their water with vitamins/electrolytes, just to be on the safe side.
A friend had told me that maybe her organs suffered damage from the infection she had. She is still the same size she was at 13 weeks. I started feeding her a scrambled egg every night, which she would gobble down.
Last week, I thought, I wonder if older pullets can get wry neck? So I got some vitamin E and started adding that to her egg. I did quite a bit of research on it and I'm now convinced that's what she has. Her head is always tucked into her body and when you pick her up, her neck gets kinda floppy. I also read that an injury can cause wry neck, so she's probably had it since the infection.
As of last night, she's no longer eating for me, I only got a couple of bites of egg in her, so it looks like I'm too late. I'm just kicking myself for not seeing it sooner.