It's not the cochin due to comb type, skin color and feather pattern, it could be 2 but she's not as fluffy and doesn't have a beard or heavily feathered legs.
Was your silkie roo bearded?
Ok, so that is not a rooster like I was picturing. He's just a cockerel chick.
It's very likely coccidiosis at this point though it very well could be something else.
I would give him a direct dose of corid.
https://www.backyardchickens.com/articles/corid-amprolium-oral-drench-instructions.74391/
I'm not sure, I really wouldn't worry about bird flu . The redness on his legs is normal for roos.
So far, the symptoms are lethargy and difficulty breathing?
Any mucus or weeping?
What's his normal diet? Anything he could have found that is toxic or moldy?
Has he ever been wormed?
Have you...