Lethargic BO Rooster Not Digesting Food in Crop, Barely Eating

[OptionC]

My Buff Orpington rooster is 4 years old. His health suddenly turned over about a 1 day period, as far as I know. He developed the following problems:

Undigested food in crop

Light green, watery poop (probably colored by bile, with lack of solids due to food not being passed down from crop)

Appetite loss

Lethargy

I've given him broth with vitamins and electrolytes and apple cider vinegar. I'm keeping him in a grassy enclosure, and offering him water with apple cider vinegar, and soft food with grit. He drank a lot of the water, but hardly ate any food.


Does anyone know what the root of the problem could be, like a medical issue? Are there any medicines I should be giving him, or any other things I should be doing to care for him?

Any help would be appreciated. Thank you.

 

[Eggcessive]

Could you collect some droppings in a freezer bag, and have a vet do a fecal float to look for worms and coccidiosis? You could try treating his sour crop with an antifungal medicine such as Medistatin (nystatin) powder found online for pigeons, and there sre other treatments here:
https://www.backyardchickens.com/ar...w-to-know-which-one-youre-dealing-with.73607/