Weak Pullet Unable to Stand Up. Previously Bleeding.

[Wyorp Rock]

Whoa! Is there something about those breeds that makes them more vulnerable to neurological issues? Is it a size thing or actually the breeds themselves?

Silkies along with other Crested birds have a hole in the skull making them more vulnerable to brain injury and/or neurological damage.
https://bitchinchickens.com/2021/04/05/vaulted-skulls-in-chickens/