I’m dealing with the same thing. And I did the same thing you are doing. I mixed 50/50 layer and flocks raiser and see the improvement. I lost a chicken that was egg bound with a miss shaped egg because they were not eating the oyster shells. After mixing the 50/50 I see the differenceAfter many recommendations from the very knowledgeable people of BYC I had stopped feeding layer feed and switched over to an All Flock product. Nutrena All Flock to be exact. I also have a feeder that has Purina Flock Raiser in it. I do have oyster shell on the side. I switched several months ago.
I have noticed the shell quality diminishing since the switch and I am not happy with it. I use to be able to toss an egg across the yard and not have the shell brake. Now just handling them the wrong way they would crack. Not all but some.
I have made the decision now to do a 50/50 mix to bring the shell quality back up. 50% All Flock mixed with 50% Poulin Grain Layer pellet. Since doing so about a week now I have noticed an improvement.
This should be a happy and healthy mix of food to keep everyone at peak performance with minimal long term impact if any.
Has anyone else experienced the same issue?