Aaannnnnd to tell the difference between the potential speckled Sussex (eyeliner winged up) and brown leghorn, check leg color. SS have white legs. Leghorn has yellow.
For the black chick, could it be a blue cuckoo marans? They evidently sometimes have feathered legs.
https://meyerhatchery.com/products/Blue-Cuckoo-Marans-Day-Old-Chicks-p212598964
Speckled sussex and welsummer look really similar BUT the eyeliner wings on a SS curves UP and on a welsummer it goes out/slightly down. Hard to tell leg color in the photo…
This may be super helpful if you are still unsure...