As I said on your other thread, the Red Sex Links sold as Sil-Go (silver/gold) normally reach point of lay in 18 weeks or almost 5 months. I do believe that slower growth and slower onset of lay is NOT a bad thing, necessarily. In fact, I brood out a couple dozen ISA Browns, each year, it also a commercial red sex link, and I intentionally slow them down.
Mine are now 19 weeks and only 1/3 are just spitting out pullet eggs. I actually prefer this. Pushing these commercial sex links into early, heavy lay isn't all it's cracked up to be. Pun intended.
None of these are "breeds". They are intentional mixes. Strains or hybrids are words also used.