My duck is sick. What are the common health problems or symptoms?

It's possible Daisy may be ill or have a deformity that is causing her to be unstable. The other ducklings may be avoiding her or picking on her because of this. If she is unable to stand upright on her own or is otherwise acting ill it is best to bring her into your veterinarian for care and to check for an underlying problem. Making sure she is not being picked on and making sure she has access to food and water until you can get to the vet may help.

These could be abscesses due to the dog bites, birds must have antibiotics after being attacked by other animals otherwise wounds almost always get infected, you will need to take her to the vet ASAP in order to get it treated.

Thanks for reaching out, this appears to be a dried wound and veterinary attention is needed, ASAP. This might require some surgical debridement. Systemic antibiotics are probably required but also protection from flystrike. Good luck.

If the neck was broken, Puddle would likely have passed away, or be in a lot of pain or distress. If she has a wound or injury on her neck, it would be best to move her to an isolated hospital cage and to treat and clean the wound so it doesn't get infected. This can help her heal without the rest of the flock picking on her and making it worse. Once she is recovered, you can reintroduce her. I would also recommend adding in some other ducks so she has friends to stay safe with. If she has been badly injured, can't move, or is in severe distress, it is best to seek emergency care from your vet or an ER clinic so she can be seen right away.

Without knowing what caused the deaths of the rest of your flock it would be hard to recommend treatment. It sounds as if some sort of contagious issue such as bacterial infection, virus, etc may be causing the problem. It would be best to bring your drake into a local vet clinic ASAP so he can be examined to determine the cause of the illness. If you have any other birds remaining in your flock, separating out and quarantining sick birds from the healthy ones, and thoroughly cleaning all shared food, water, bedding areas may help reduce further spread.

I saw you asked this question twice, so I'm reposting my answer for you to ensure you get it! It's possible Puddles could have an injury or infection of the foot. Ducks and other fowl can easily cut the bottoms of their food, leading to Bumblefoot, or a bacterial infection that causes pain, swelling, redness and inability to walk on the limb. Breaks or sprains in the leg can also cause a limp. Other issues such as nerve or muscular issues can also cause a limp. If the limp continues, or you see signs of infection such as swelling and redness, seeking veterinary care to have it treated is best.

Poor Lizzy! It would be best to remove her from the flock and thoroughly clean the foot and leg (as ducks love to get mud on their feet!) so you can check it for any visible injuries and wounds. If there are any wounds, keeping it clean and dry and using something such as Blu-kote can help while it heals. If you can't find any wounds, see swelling, or the foot looks badly infected, it would be best to have it checked out by a vet in person. Keeping Lizzy separate from the flock until she is healed can help prevent the rest of the birds from picking on her. Keeping her confined with easy access to food and water while you treat the foot can also help reduce any further irritation to it while it heals. However, if it isn't improving or seems broken/badly injured, vet care is needed.