Frizzles also don't insulate as well. And mites or lice will cause severe, fatal anemia!!!
Permethrin spray or dust, if you can get it, or spinosad also works. If it's legal to use ivermectin on poultry where you live, it also works well.
Mary
Any mites or lice? Look at night with a flashlight for them. Diet matters a lot, and access to food and water. Are there multiple feeders and waterers, so nobody is excluded?
Cold, yes, Silkie feathers aren't as insulating as 'normal' feathers, and these chicks may need added heat, or at...