I used to feed a layer and saw problems feeding it such as egg shell quality, and protein deficiencies since I like feeding a bit of scratch daily. When feeding a layer they shouldn't be fed extras as it cuts the daily protein down. I find an All Flock and oyster shells a perfect diet. If I'm...
Actually you should still put out oyster shells when feeding a layer as some hens need more than what's in the feed and some need less. Those on layer will eat the oyster shells at a decreased rate, and generally only if they crave them.
Are they new layers? It can take months for the glitches to work out of the system.
I have found hens fed a layer are more prone to calcium deposits and other egg shell issues. Sometimes they get too much calcium from a layer ration which is a one size fits all mentality. I feed an All Flock...