I cannot help you with the cause. Hopefully someone else can and that might help you with your decision.
As far as culling, as long as they are healthy and not suffering, I'm usually slow to kill them. They could easily outgrow it. If they are suffering and not thriving, that is a different story.
I don't know why you are raising chickens and how it fits into your plans. With my set-up and goals, I would not let these chicks breed, even if they did recover. I would not want these traits in my flock. My preferred method of culling would be a frying pan, stew pot, or the oven. If you are looking for a pet or am egg layer only, not a breeding bird, these may work out fine for you. Depends on what you are after.
Hope this helps some.