The Red NN could still be a cockerel, just a quiet one!
Likewise, hens can crow in certain situations, though usually when there's a lack of a rooster.
Have your roosters established dominance yet? It's likely that the black one (if indeed a rooster) is higher in the pecking order than your Red NN, hence why he feels confident enough to crow while the NN doesn't.
In truth, four girls to two boys is a little much. We had two roosters to 10 girls and they still got over-mated, with bald backs. There are some situations in which the numbering could work, but that all depends on rooster personality. More realistically it'd be best to get rid of a rooster, or get more hens.
Of course, this all depends on if you keep them together 24/7, as well. Our roosters are separate from the hens and only allowed out with them during free range.
Rough that you'll have to be rid of them after this long, but good on your seller for being willing to fix it. The more I look at CottN the more I'd bet actual money that she's a pullet. Also, curious as to what breed Hawk is. Coloring is beautiful! Redd is a roo if I ever saw one, but can't really say on Turk. I'm not very familiar with turkens I'm afraid, so can't say for sure, but despite Turk's big comb I can't shake how much she/he reminds me of one of my hens, also with a large red comb. More certain with CottN and Pebbles, but I'd hesitate to call Turk a roo as well.