I don't know what's wrong with my hen! She is a 6 month old silver laced Wyandotte and can't really walk or stand and can't lift her head! Every time she tries to lift her head it just falls back down limp. I went to the feed store and they said to give her nutri drench which I have given her twice today. Yesterday she was fine and running around like normal then when I saw her this morning I thought she was dead! Please help she is my baby and I'd hate to lose her!
First step is to isolate her in a location where you can provide good supportive care (preferably indoors) - the area should be quiet, dark and calming and she needs to be in a safe containment unit (cate, crate, tote, etc). This will allow you to better monitor her, identify symptoms and provide treatment while also helping to protect the rest of the flock (though, honestly, at this point they have been exposed anyway).
Now, tell us how she is laying - is she in a normal "nested sort of position or is she on her side with legs outstretched? If you pick her up and hold her a bit above the ground does she try to extend her legs, pull them up under her or do they hang motionless? Is there any discharge from her beak, nares, eyes or vent? How does her crop feel? What is the color of her comb and wattles? Are her eyes bright or dull, clear or clouded? Is there any odd odors (ie foul) from her beak? What does her breathing sound like?
OGM has given you good advice. Three things come to mind-- dehydration, possible Mareks disease, or possible botulism, which comes from eating a toxin found in dead animals or rotted vegetation and maggots. Botulism tends to cause paralysis that starts in the legs, then moves upward to the wings, and then to the neck. I would try to get her to drink some water with vitamins and electrolytes from a cup or with a dropper if she is alert and can swallow. Was she vaccinated for Mareks. I hope that she starts to feel better, and please update us.
It sounds a lot like Mareks, but some vitamin deficiencies can cause neurological symptoms as well. Keep up with the vitamins, but since PND does not contain riboflavin (vitamin B2) I would give her a small amount of egg. liver, plain yogurt, or ground nuts which contain riboflavin (just a small amount will help.) Also keep in mind that coccidiosis can cause similar symptoms from dehydration or electrolyte imbalance. Diarrhea or blood in droppings, hunching, poor appetite, and lethargy are signs, and Corid (amprollium) is the treatment.