Chicks who once have pasty butt may get it again for the first week to 10 days, so check it daily and clean off with soapy water. Hopefully you can revive this chick by dipping it’s beak into water with electrolytes, or water and giving a couple of drops of Poultry NutriDrench. Silkies and other bantams always seem a bit delicate to me for the first couple of weeks. Once they start to show symptoms like this, possibly from the shipping stress, it may be too late. But I hope that you can save it. Having it is a brooder with bigger and a little older birds may well have exposed it to coccidiosis, so it wouldn’t hurt to start Corid later today. But I would try to get some vitamins and electrolytes in it first. Thiamine or vitamin B1 should be stopped during Corid.