Trust your gut. If you think he's not feeling well he's probably not.
Have you ever seen a sick peacock display? The fecal was clear so no worms, if Blackhead he would have succumbed to it by now since she said three weeks. I guess some slow-moving problem like cancer or some internal damage if we are grasping at straws, nothing that can be treated. Maybe even ate something sharp? I think most likely it is seasonal hormonal changes.