one of our roosters, arnold, has been acting funky the past few days.
it started out as he was limping accross our driveway about five days ago.
we brought him inside so he could rest a few days since our ducks had been picking on him.
he ate well for the first day and then his droppings started turning bright green and we notcied today his comb is turning a dark purple color.
he has lost most of his appetite and he doesn't want to stand on his own.
what would you suggest?

please help.
he's our favorite.