If the flock they're going into is relatively gentle, I usually add more dominant animals one at a time, let them spend a few hours without buddy backup, then add another one.
It certainly seems suspicious for something they were carrying before they got to you. I'm just putting the toxin theory out there, but I agree with the previous post.
My BBW turkey poult has a dislocated knee joint. I made a half-cast and put him in a sling suspended from a kennel crate, and just because by now his hip is out too, I taped his legs together.
His food and water are available all the time, and the other birds can't reach them. I plan on leaving...
Would it be possible to isolate the hen sitting on the nest so that the others can't disturb her? If you were able to do that, I think I would return the eggs to her.
It's so encouraging to see 5/5 babies actually hatch! I know it's commonplace for a lot of people but I'm so excited! I literally had no luck with the Styrofoam incubator.