Have you treated them all for shock? That's step number one. Prepare one teaspoon sugar to one cup warm water with a pinch of salt and baking soda and give it to all of the chickens involved in the predator attack. Shock can cause leg weakness among other symptoms. It can be life threatening so give the solution for the next several days.
A chicken that is injured so badly that they lie down with eyes closed and won't move would qualify for euthanasia. Any chicken still able to eat and drink and move about, even with leg weakness, has a chance to recover.
Here is my wound care protocol.
1. Treat for shock as the number one step. Give warm Gatoraid or mix the solution as described above. Have the patient drink it all or syringe it into the beak. Dip the beak to show the patient it’s sweet.
2. Flush the wound well with saline. This is better than soap and water as it maintains the ph balance of the tissues. But warm soap and water will do. You need to wash away the bacteria from the wound. Scrub away all blackened or dead tissue.
3. Inspect the wound carefully. If it has a skin flap dangling and it’s still pink and warm to the touch, keep that. Do not cut it off. Look for bite, tear or puncture marks indicating a puncture wound. If you see this, the patient will need an oral antibiotic such as amoxicillin. Bacteria from the predator’s mouth can be injected deep into tissue and can kill in as little as 24 to 48 hours. You may want to try to obtain some amoxicillin from your vet to treat the bacteria that may have been left behind in the puncture wound.
4. Use a topical antibiotic ointment such as Neosporin, triple antibiotic ointment without pain killer in it to coat the wound. If there's a skin flap, lay it across the wound that has just been coated with the ointment. Then smooth on a generous amount over the top of the skin flap to hold it in place. Manuka honey is also a good wound treatment for a large wound and will keep it moist.
5. Gently scrub the wound every day with a soft wash cloth following the above steps. This will get rid of any non-viable skin cells that will attract and support bacteria. Keep the wound covered with the ointment. Never allow the wound to get dried out or it will not heal.