Lethargic rooster

[RBGChicks]

My rooster seems sick and I am hoping to get some opinions on what is wrong and advice on how to treat him:

Symptoms:
-Noticeably lethargic for the last few days - sleeping/napping, not interacting with the other birds as he usually does, moving around but only if he really needs to do so
-only crowed once in 2 days when he normally does this several times a day
-Not eating much. Eating, but very small amounts. Napping over the food dish and then pecking at it when the hens are doing something else.

Other observations:
- no visible injuries
- poop looks normal (not runny)
-no coughing, wheezing, or sounds of breathing issues
- no other chickens appear sick

We isolated him yesterday in an impromptu rooster infirmary (cage) and put him some favorite foods (scrambled egg, cracked corn) plus extra olive oil and water. He ate a bit but not much. He seems to neither be getting better nor worse.

Any ideas?

 

[RBGChicks]

Just to add - his comb looks normal but tail feathers have been mostly down the last few days

 

[Eggcessive]

How old is he? Is he having any problems walking or getting up? Look for any nasal or eye drainage, wheezing, or sneezing. Check his crop to feel if it is empty, full, doughy, puffy, or hard. Look his skin over under his vent, wings, and on his neck for tiny bugs lice or mites, or their eggs. Feel of his breast bone (keel) for weight loss. Get some Poultry NutriDrench or Poultry Cell vitamins, and give him 3 ml daily. Push the fluids, and keep offering food he likes, as long as his crop is not impacted. I would keep him in a crate on an old towel or paper towel to look at his droppings. If a vet will examine his droppings, you could check for worms, cocci, or enteritis.