Rooster with lethargy and droopy neck

[SpringWolfie]

His neck isnt turning to the side and he occasionally lifts it up. He made a small poop with a whistling sound before he pooped, no blood or parasites seen in poop. No visible injury, eats and drinks if food brought to his beak. Was found standing completely still outside and didnt run away when approached. One of his hens is already inside recovering from vitamin deficiency and struggling to walk- so its not impossible that he also has this.

Fed him oats and water, and noticed afterwards thick white mucus

Would much appreciate insight and tips