Speckled sussex hen, rooster, or something else entirety!

[Steviechickie]

Tractor Supply mixes chicks up all the time, and they'll move leftovers into brooders of new varieties they stock.

Black sex links are a cross between barred rock and RIRs, not partridge rocks. I'm not 100% certain yours is a partridge rock, but the resemblance is strong. I'll post an online pic of one for comparison.
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Oh wow they are very close