Sorry I wasn't very informative.
A comb is the red fleshy thing on top of the chicken's head. Comb size and shape vary between the breeds. Most people are familiar with the 'single' comb which looks like this:
But some chickens have a 'rose' comb, like this:
It's flat on top.
Other's have a 'pea' comb:
It has three ridges along the top, but isn't as tall and thin as a single comb.
If I were to guess I'd say your hen's are mixes, possibly Buff Orpington, maybe some Barred or Partridge Rock in there. With the possible exception of the 2nd hen from the left on the last photo, she could be pure Buff Orp.
A sex-link is a first generation cross between two breeds, the female offspring are a different color than the male. There are many different breeds that can be used to make sex-links, a Buff Orpington male with a Barred Rock female would produce a chicken that looks like your buff and black hens, unless, they have rose combs. A rose comb would indicate that they have a different parent.
Hope this info helps!