I have a sick chicken (or two) that seem to have a lymphoma virus (or something like that). Their poo is yellowish, their abdomen is fat and puffy, their feathers are puffed out, and they aren't moving much. I can tell they are miserable. How can I euthanise them? I don't want to snap their necks and I don't have a gun, nor would I want to shoot them. What can I do?