That is how Welsummers feather. They very well may be Sussex, but if they do turn out to be Wellies, I doubt you will be disappointed, they are good layers and have beautiful dark brown eggs your customers would love to see! Mine have freckles on most of their eggs too, which is an added bonus. They are very calm and easy to handle birds too. I love my Welsummer roosters for how well behaved they are too. They don't tear up the hens nearly as bad as the others and they have never been aggressive toward people, plus they are gorgeous birds, see:
She has a coarse looking head, but she is my biggest Wellie girl. I think she must be the momma to that rooster, he is a big boy for a Wellie - actually closest to the right size and weight of any of the Wellie roosters I have raised, I think.
The bad thing with my Welsummers, my old rooster who was 4, when he molted last fall, went from looking like the fella above to this: