Man my girls are holding out. We have 4 different kinds that are all about 19-20 weeks and nothing. I put an Easter egg in one of the nesting boxes and they have moved it but none of them have shown much interest in it. Well except staring at it and shreeking. Especially the leghorn. I think she's bipolar. Lol
Mine are pretty close in age to yours. A few are younger. Mine are pretty unimpressed with the nesting boxes too.