It is possible for a chicken to start laying at age 16 weeks, but most start laying much later. Your EE and Cochin will probably be later than the others. I had 23 pullets. You can se the breeds in my signature. The first one started laying at 18 weeks. Two weeks later, two more started. In another 2 weeks, two more started. So I had 5 out of 23 laying by age 22 weeks, but I had 18 that were not laying. Most had started by age 27 weeks. It will vary quite a bit by individuals even of the same breed, but maybe you can get a rough idea of what might happen by what happened to me. My better layers were the ones that started laying a bit later, so there are some advantages of not rushing it too much.