One of my Rr cocks I have in with three hens and I am getting 1/6 ratio of SC offspring. I am guessing it maybe one of the hens is also Rr....interesting tho that it seems selective for which rose combed breeds it affects...
the rose comb dorking breeders (red, white and colored varieties) I've asked haven't had any single combs pop up, nor do they have fertility issues.
The other Rr cock has three hens and I have not gotten any SC offspring.