I also would not worm him at this time since he seems weak from not eating and drinking. That can cause green runny poops. Instead of Poultry NutriDrench, I like Poultry Cell. It has the same ingredients plus riboflavin. Dosage is 1 ml per every 3 pounds. Hopefully, this is not Mareks, but just another illness or weakness. Pick him up often to see if he can walk, to look at him for injuries, and to exercise his legs. Chicken slings, which you can Google for pictures, are sometimes helpful to get chickens up and out of their droppings, and to reach food and water. If used, removed him often, and let him sleep on the ground.