I have a female khaki campbell with a droopy butt. Don't know what's wrong with her. Had another male duck maybe ten years ago looked similar before he died. She is probably considered very old for ducks. She is slow to move. Still seems to eat and drink, just not as much as she used to (or maybe just slower than usual). I have her sister approximately same age no swelling or droopiness in that area. Could it be worms? I'm worming them now. It's been going on for about 5 days now. Any help would be greatly appreciated. I don't want her to die, but I know she is very old.