Okay, then I'd probably just follow through and try the Apple Cider vinegar mixture, my friend used ACV with some herbs since they have their own healthy properties as well to help.
I hope this will help for your silkie peeps, keep me updated to see if there's any progress or an other ideas!!
Any new treats or feed being introduced?
But if not, and this behavior keeps continuing ide suggest an apple cider vinegar mixture since ACV is great for gut and crop health along with having prebiotic and anti-fungal properties.