In the calculator, for the Speckled Sussex use Wheaten, Columbia, Mahogany, and mottled. The mottled will me lower case since it is a recessive gene.
For your white chicks, I suspect they are not white but instead are Splash. That would come from your blue chickens. The blue gene is one of those funny ones that can easily mess you up, even after you think you have a handle on it.
If a chicken is pure for the Blue gene, you get a Splash. If it is split for the Blue gene, you get a blue. If it does not have any blue, you get black. That sound straightforward enough but…..
The blue gene only acts on black. If otherwise the chicken would be pure black, then the chicken will be Splash, Blue, or Black as determined by the Blue gene. But if the chicken would otherwise be buff, red, or white, you would not see the Blue gene at all. If normally the chicken would be a different color but have black pattern feathers, like a black tail, then only the pattern, in this case the tail, would be blue.
Take a Speckled Sussex feather for example. With no Blue genes, you have a red feather with a black band, then a white tip. If there is one copy of Blue, you would have a red feather with a blue band, then a white tip. If it had two Blue genes, you would have a red feather, a splash band, then a white tip.