Yes the ones in question do not sound like a roosters crow it sounds gurgled. And they sit in the nesting boxes and make egg laying noises as well. I know that my RIR that I had in washington all had a defined red comb that popped up much later in development than the rooster. My RIR roosters were very well defined by 16 weeks. I am not familiar with the breeds that I have. And while I am constantly researching them I am in uncharted territory with them.
Yes every breed is a little different, and some are hard to tell until they are older. I've been fooled early on more than once. Worst case scenario, you wait until you are sure. The signs will continue to grow as they do. Just have a plan for those in case you don't want that many cockerels. Young cockerels will sound dorky crowing until they figure it out, hens kind of always sound dorky, at least mine have.
I also said I suspect that one may be a pullet, but the picture isn't good enough to be sure. Time will tell!That picture of 3 you all are saying contains only cockerels, I think that there is a pullet, its the one farthest to the right out of those three.