At the age of your chickens, hackle and saddle feathers are not going to help you separate the cockerels from the pullets, as those develop later on. Also note how #5 is just know starting to get his tail feathers and finish up losing all his chick fluff, this is one sign of him being a cockerel...
What beautiful Chickens! Congrats on your flock.
1. White Crested Black Polish pullet
2. White Plymouth Rock, leaning towards cockerel
3. White Orpington pullet
4. Leaning towards a Dark Cornish and cockerel, possibly a pullet.
5. Production Rhode Island Red cross, leaning towards cockerel
6...