White Sussex - what to expect?

[Goingsolo 24]

I'm still in my first few months of chickens and need advise please. I got fertile eggs from my sister - they were white sussex hen x white Sussex rooster. The parents were bought as "pure" bred apparently. I've attached a photo of the chicks. My question is: Why do some chicks have black on their wings and others not? What should the offspring look like at 2 weeks? Where should the black or "white" be? Bottom photo is of the parents.(I'm not referring to the Motley white/brown chick)

 

[Mosey2003]

I would say it's probably just differing levels of the black being expressed. Some will have more or less on the wings and hackles, etc. Probably will change with the first molt anyway. But, I'm not a Sussex or Columbian color expert.