I think all three of the light Sussex-marked birds in the pic are males. The middle one has the fuller tail of the three, and seems the more advanced/dominant, but the others are not far behind. The outside two have signs of developing sickle feathers. None of them look like females. Closer inspection of the legs should reveal bumps which will be the start of spur growth.
Even in breeds where the males are fairly tolerant of other males in the flock there will always be the potential for trouble when one bird is treading, particularly with young birds and where none are completely dominant yet. It's probably the one time when the treading bird is at a disadvantage as far as self-defence goes, so other cockerels will take advantage of that.
The heads are another give-away, being heavier than one would expect in a LS hen. Also, the combs on all three birds are not correct for pure LS; that, and the stance, particularly of the middle bird, would suggest to me that they perhaps have some Wyandotte in their breeding.