New young rooster just sitting on the ground

[freebornman]

I have a Light Sussex rooster, 18 weeks old, a beautiful bird who has taken a down turn three days ago.
I bought him along with a hen who never leaves him, although she does so when hungry.
He just sits inside the coup, not on the roost. He came out briefly today and drank some water but not eating. I have six chickens altogether and they seem ok. He has been so active since I bought them both last March. The coup is large and cleaned out regularly. I use wood shavings for bedding. It’s hard to determine his poop from the others but it might be runny.

 

[BigBlueHen53]

Please post a pic of the rooster. Try to get him in good light as color of his comb and wattles may be helpful. Can you pick him up and feel his breastbone? Is it sharp and pointed as if he has lost weight, or does he feel well padded? See if his crop feels like it has food in it before bedtime tonight and then feel it again in the morning, first thing before he has a chance to eat or drink anything. It might be helpful to put him in a dog crate overnight for this purpose if possible, inside the coop, and maybe put paper towels or newspapers under him so you can get a picture of his poop. Is there any odor coming from his beak?