thanks for that great information! purina doesn't have a grower i am feeding there starter/grower i think i said starter on accident but i meant starter/grower. i have a white leghorn, buff orpington, olive egger, 2 easter eggers, black copper maran, and a black austrolorp. i asked on another thread and pretty much everyone said not to go to a layer because if i ever want to get more chicks when i introduce the new chickens they would eat the layer when they do not need all that calcium or if you have a rooster i it does not lay so it doesn't need all that calcium. what are your thoughts on this??At that age, they should have moved to chick grower by now. When they will come into lay depends heavily on the breed. If they are your typical sex-link egg laying machines, then around the 18 week mark is accurate - could be a few weeks before or after, but 18 is the average. For heritage breeds, you will be waiting a bit longer - average is 24 weeks.
If they are sex-links I would strongly recommend putting them on a pelleted feed which includes calcium around 17-18 weeks and start offering oyster shell in a side dish now as they will not over-indulge. An egg a day is very demanding on them and you are likely to run into nutrition issues with just loose grain feed and calcium on the side - they're like people and don't always eat what's best for them :/ There's a bit more lenience with other breeds that lay less as they aren't expending so much on keeping egg production up.
If they are roosting consistently, you can make nesting boxes available now with fake eggs as they will investigate and remember this as a safe place to lay.
You should notice a distinctive shift in their behavior when they are getting close to lay. All of mine went a bit stir-crazy, were anxious constantly, became much more vocal and wanted to explore outside the run as much as possible. When they are a week away from starting, you may see them exhibiting lordosis, or 'squatting' behavior.