First of all, I would recommend calling your local veterinarians and asking them if they can treat chickens. A vet doesn't have to just be an avian vet to accurately diagnose and treat chicken diseases. My local vet treats all sorts of animals and also treats my chickens and ducks, with great success.
It sounds like your Silkie with the neck issues may have a nervous problem known as wry neck. There are several causes of wry neck, but the fact that your bird is a Silkie is very suggestive. Here's a quote from an article in The Poultry Magazine (Vol. 4, Issue 1, May/June 2013; "Wry Neck in Chickens" by Katharine Jennings) that may shed some light on the issue:
Quote:
As to treatment of such trauma, the article is not very helpful and suggests using steroids (I think the article is written for poultry vets). However, it did mention to isolate the bird from the rest of the flock for its own protection, and to keep an eye on it so that it does not drown in its water dish (something that can happen if the wry neck leads to paralysis). Again, contacting a local vet on the issue may be of invaluable help.
Another thing that can cause wry neck, according to the article, is nutritional deficiencies, and sometimes even poisoning of some sort (such as from pesticides or other household poisons that are so common that they are often overlooked). Make sure that the feed you're giving them is high in necessary nutrition, and that potential poisoning sources are not present.
As to the other chicks, how many have you lost? Was there any warning at all, any strange behaviors? When they are that young, there can literally be a host of diseases that could kill them quickly...unfortunately, young birds are the most susceptible to lethal diseases. Any specific information about your flock, including housing, access to the outdoors, etc., would definitely be appreciated and may help me or someone else give you a better idea as to what may be happening.
I hope you don't lose anymore...keep us posted!
~Gresh~
