Just an update: I took her out and let her out on the grass so I could change her bedding. Fortunately her digestive system is working because I found she was lying in her own poo and lots of it was also buried - I saw none the past few days so I was worried she wasn't able to.
Her 'condition' seems very strange and may have worsened. When I approach her, touch her, or she is otherwise stressed or scared, her neck and back convulse, her body spasms, and her legs flail, sending her flying over end, usually landing on her neck and head. The 'fits' as quick and she is fully awake and doesn't seem too bothered by them, as she goes back to eating when she's done. She ended up landing on her side in some mud which is why she will look dirty in the little video I got trying to show the tremors in her legs. I wasn't able to get one of these 'fits' on the video though, but a few minutes later she had another, small one, as she tried to flip herself over.
I saw her preening herself, but also ripping out her own feathers and eating them. I instantly wondered about her protein levels, so I scrambled an egg and gave her a few pieces, relieved that she was able to eat them. She was quite happy to eat them, too.
Out of curiosity I found this article about vitamin deficiencies in poultry: http://www.nap.edu/read/2114/chapter/9#49
There are neurological symptoms similar to what our hen has, such as Convulsions with hyperexcitability, characteristic fright reaction with tetanic spasms, bottoms of feet rough and calloused with hemorrhagic cracks.
It may be coincidental but I will keep feeding her eggs to see if there is any improvement, and will try to find a poultry mineral and vitamin booster for her to see is that helps as well. It won't hurt her if it doesn't. Would nutri-drench be recommended? Psycho is not interested in any way in drinking water. She dipped her beak, shook her head, and did so twice before turning away. I don't know why she doesn't want to drink. Hopefully she was able to get liquid in the watermelon and grapes I've been giving her, as she refuses to drink her water.
Our chickens have been on the same feed for the 4 years we've had them, the Extra Egg Blue Seal poultry feed, and have never shown many signs of trouble. But she no longer lays and her dietary needs may have changed. We have had chickens eating eggs in the coops as well.
I couldn't add an attachment so I uploaded it to youtube as a private video. Not the best video, unfortunately. I'm not too great at handling a camera.