Gold sex link or called Comet chicken. They are 100% sex determined at hatch by color difference of males and females.
The barred birds are hatchery Barred Plymouth Rocks. It doesn't hold true that the lighter birds are males with hatchery stock. Though you've a lighter (larger white bars) bird or two they still look like pullets to me at 4 months of age.
Well,at 4 months pullets shouldn't be devoloping any combs.And clues are the comb the tail the body.The combs a lightish/darkish color.Cockerals start getting that on combs so that's your first sign.But I would believe at 4 months it would crow.But still its tails kinda curly.And its pretty big.I'm gonna go with a cockeral on number 2!Not only,but am i mistaking.Is that SPURS?
The biggest looks like a rooster as well.The other 1 looks more like a hen now that i get into it.It looks like a couple.Im sure of your Sex link.Shes a pullet.