Those look like males to me. You could try posting them in the what breed and gender forum for some more opinions.
I have a lot of mature roosters running around so the young boys are more wary, and often don't crow until they are a bit older. It all depends on the breed too with smaller breeds...
Most are fully feathered at around 5-6 months, but some may take longer to grow in their tail.
They can crow anywhere from a week old to a year old. Most start to crow at around 4-6 months in my experiences.