I had one freedom ranger chick awhile back who has strait blood dripping from her rear with each poo. She already had a round of Corid and it didn't stop, so I gave her 1 dose of safeguard and sperated her for a week with nutridrench in her water. She recovered completely. I am thinking it was worms or some injury. She didn't have any external wounds tho.
Not sure if it will help your silkie, but worth a shot if no one else responds.
@PurpleCArTires has a good suggestion. Worms can also cause erosion of the intestines so adding a wormer to the Corid won't hurt.
But you can also add a drench dose of undiluted Corid to the treatment for the next three days. Syringe a straight dose of Corid at .1ml per pound, so if this is a very young chick, .1ml would be adequate.
I gave mine 0.23ml per pound of weight orally. I used goat dewormer.
I did only 1 treatment, but I think it's recommended to do it again 10 days later. I just didn't do it because she was a small chick and was "off" the day after the first treatment. I think it was rough on her little body.
She recovered completely, and I keep a close eye for more blood, but nothing since treatment