What breed of chicks are these?

[MotherOfChickenss]

I have 4 total. 3 of these little yellow chicks and 1 black with white wing tips. She’s way smaller than the other chicks.

 

[TheFatBlueCat]

It's pretty tricky to tell, where did you get them from and does that narrow down the options? I would guess the 3 golden chicks are some sort of red sex link. The little penguin chick could be anything, she/he will be black or some kind of black based with markings (my barred rock chicks have this pattern when hatched). Possibly a bantam breed since it's smaller.