My RIRs are 22 weeks and only 8 out of the 11 are laying. It is easy to tell who is doing the work. Three have very small pink combs and eight have much larger bright red combs. I was very surprised at the difference in development speed for birds that are the same age! Good Luck!
Buffs only- mine did the same thing! Surprised me at 19 weeks. They took to laying on the floor in the litter. I put the nest box in to no avail. Then I tried three golf balls in each box for one week. It works like a "how to" or in this case a "where to". I have not found one outside the box...
My 11 RIR started laying 3 weeks ago. We'd get one egg, then three, then two. Now we are collecting between five and eight every day. At least three still have not laid anything, but they sure are cool to watch! The egg laying takes a while for them to adjust to. Be careful what you wish for...I...
When my RIRs started laying, wee had one egg that was covered in "skin" instead of shell. It was totally gross feeling. I added oyster shell (calcium) to the feed and haven't had another one. Good luck!
Our flock started laying 3 weeks ago in the corner of the coop. I put 3 golf balls in each of the nest boxes. I haven't found one egg on the floor since. I left the golf balls in the boxes for one week until I was sure they were trained to it. Good luck!