Hello there and welcome to BYC! Looks like they are molting. Molting can take a couple months to complete. You might also give them a once over to make sure they are not carrying any mites or lice, however it looks to me a like the fall molt has taken over your flock! Giving them some cooked ground turkey or beef a couple times a week can help them get through the molt a bit quicker and easier. Molting can be very hard on birds. Enjoy your Silkies and welcome to our roost!
Hello and Welcome To BYC! X2 what TwoCrows said, looks like pinfeathers coming in and is molting. Nice article on it http://www.thepoultrysite.com/articles/217/moulting-a-natural-process
Welcome to BYC! Please make yourself at home and we are here to help. X2 she is molting. They often begin at the neck and work downwards. Depending on the breed, it can take anywhere from one week to three months to finish the molt process. Protein is important during the molt. Foods such as quinoa, meat scrapes, fish, mealworms, etc should all be fed while the chickens are molting. Feathers take up 85% of their protein so losing all their feathers means they will lack protein. If you see your flock eating feathers then they need more protein. Also, watch for bulling and feather picking during the molt. Sometimes chickens peck at the bald patches on the molting birds so it's important you watch out for this. If you come across an injured bird, isolate her, clean her wound, give her herbs and let her heal. Good luck!