Breeding birds need a high quality balanced diet in order to produce healthy strong eggs.
As for the calcium, I leave out dishes of oyster shell 365 days a year. The hens will eat it if they need it. You can judge the calcium in the diet by the quality of the shells. If shells are not thick and hard, the diet is low on calcium and maybe low on vitamin d as well. Or else the calcium phosphorus ratio is off. If eggs all have thick hard shells, then the birds are getting sufficient calcium.
Grower is probably too low on calcium for laying. Especially if that is chicken grower and not turkey grower. It takes a lot of calcium to build all those egg shells. By letting the birds eat what they want, they will balance their intake for you.
During laying seasons, my birds eat oyster shell like it is candy. Fortunately, it is really cheap to buy.