Self-feather pecking and soft shell eggs

[JoCin]

Is she eating a regular chicken feed as well? If so what's the protein percentage on it?
I would cut out the scratch for now and up the protein in their feed to 20% in case it's a nutrition issue. You can also try pinless peepers as well to see if that discourages her.
How big is their coop and run? Pictures would be helpful

 

[FrostRanger]

Your setup looks great! What I would do at this point is do one last check for mites or lice both both on the hen and on the roost and assuming that comes back clear, try the pinless peepers