One of my hens has exhibited episodes of leg weakness and a dropped wing. This has happened three times in the past few weeks. It was so bad that I thought that we were going to have to put her down. We gave her some Poultry Nutri-Drench last night and within minutes she had perked up and was able to drink some water and eat some pellets. She appears to be in decent shape today. Does anyone have any ideas what would cause the extreme leg weakness, dropped wing and inability to move?