Welcome!I feed mine later pellets and scratch mixed together. I have oyster shells in a separate feeder. I'm getting 1 to 2 soft shell or no shell a day. I'm gonna try mixing the oyster shells in with the pellets and see if that helps . I've never had this problem until I got some new full grown hens hens from the feed store
Please stop mixing scratch in with the layer pellets. You are preventing them from getting a balanced diet.
The layer pellets is formulated as a balanced diet.
By mixing it (layer feed) with other stuff you are taking away from it being balanced.