Sick 3 week old Pekin duckling.

[HomesteadGeek]

This is Henry our sick Pekin duckling. He's a little over 3 weeks old. We're not sure what's wrong with him. He was fine until 4 days ago when we found him lying on his back. His neck, back, and legs seem rigid and fully extended. His mouth opens and closes constantly. He's currently isolated and we're helping him drink and eat. We're still at a loss as to what it may be. Hepatitis, botulism, and nutritional deficiencies were some possible things we found online. We're giving him vitamin droplets, apple cider vinegar in his water and brewers yeast in his feed. Also we gave him a dose of activated carbon today so we'll see how he fares. If anyone has ideas of what he may have and what we can do to help him, please let us know. Thanks!