it is a mareks problem and some birds you brought on the place must have had mareks and are sluffing off the disease
just as the ones that are cripled
I would guess that the silkie was exposed to mareks
silkies have several issues that will reappear when put on new ground or with new birds
so...
mareks will effect young bird and old birds
especially when they have very hot climate or very cold climate
and they do die suddenly as you will not notice their trouble walig till it is too late
***The person telling you what the vet tech said is true on vaccinating the chicks
and if one chick...