Thank you for the tag
@Certified Chicken Lover
I am no expert but do know about my silkies.
By now you know, this is most likely a vitamin deficiency. We give ours Poultry Cell in their water about once every week or two, or whenever one starts looking awry, but with the issues as bad as yours, I'd have followed their directions and used a syringe to give it direct, then in water after that.
Having rats around your coop is going to make mites a never-ending problem and mites can take a chicken down too.
So, here's what I do:
These are on Kalmbach's crumbles with a dish of oyster shell on the side.
We use DE in the coop as because, like you, we have mite/chipmunk issues, but the difference is I'm guessing is that we religiously use it bi-monthly and we've never had mites albeit scaly leg mites three times now. I would never treat your mite outbreak with DE though, same as I didn't treat scaly legs mites with it. Try permethrin dust (this comes in a spray too that you could spray the coop with if you rather), garden dust, or elector psp, or if in the UK, Exzolt. We also added a barn cat who ended the chipmunk issue.
Cutting down the cedar trees could be causing some issues too as some of what could be considered toxic becomes airborne. If that fresh cut cedar is in close proximately of the coop, I'd move it.
I also ferment Kalmbach's Henhouse Reserve and 6-grain scratch which gives them increased vitamins/minerals plus probiotics and prebiotics, and grow hard red winter wheat sprouts in the winter.
Silkies are more prone to vitamin deficiencies than most chickens so to ensure we're covering all the bases with them, we also sprinkle a small amount of Rooster Booster granules in with their crumbles.
I hope some of this helps and I hope your silkies return to full health asap!