Those are all dual purpose chickens that will do best with at least 18% protein... since layer has only 16% I never use it!
I suggest using a grower with at least 18% protein or my preference is flock raiser with 20% protein... oyster shell offered free choice on the side starting around 16 weeks and they will use it as needed. Calcium and protein content are the two MAIN differences in ALL the formulation regardless of what confusing term they are labeled like all flock, starter, grower, raiser, broiler, and so on.. If they are as broody as their reputation.. flock raiser will also serve you well if you add chicks.. everyone eats it all the time here.
Very few birds will start to lay by 16 weeks. Orpington are little slower to mature in my experience and if you add time of year (at least here) I wouldn't expect laying before 24 week but likely later. My Rocks often start around 20 weeks... but it can depend on breed, individual, nutrition, and daylight... laying hormone is light triggered once maturity has fully set in.
How cool to get a different one!
