Four toes along with single combs would verify the birds are cross breeds. Genetics as it is-pure silkies do not have the genes to produce either single combs or four toes. While the toe number may be a fluke, single combs on two birds are not. I've had silkies with some really weird combs but never a single comb.
Those bantam silkies are beautiful; looking very healthy.
Single combs on hatchery quality silkies are very common.
It shouldn't be but it is. I see nothing with those birds to point to cross breeds but I do see a couple things that point to poor quality hatchery silkies.