ive got the same problem. just started in march as they started to lay good again. usually i can stop, them buy putting the fake ceramic eggs in their nest. not this time. there's yolk and shell fragments all over in their nest boxes. i got rid of the r.i reds that were in there because they weren't laying much since last year. i was hoping it was them, but it wasn't. now there's copper marans and easter eggers in there. ill have to try the mustard trick. 1st time in 45 years or raising chickens that i haven't been able to stop this.