Help sexing 4 chickens

[Short Round]

Hello, like many others I have come here to hopefully find out the sex of my chickens. We are new to owning chickens and are having a difficult time figuring out the sex. I am fairly certain 3 of them are roosters just by going by comparison infographs on the internet. They are 15 weeks old.
I see 3 of them have very defined combs and the sickle feather. I don't see a spur on any of them. These are mixed breed chickens.
If more photos are required please let me know.

Thanks!

 

[rural mouse]

You have 4 roos. Some handsome ones at that. The all white is slower developing, but the pointy cascade of feathers in front of his tail is unmistakable. The red patches on the shoulders of the other 3 are a rooster only trait as well.

 

[SilverBirds]

All 4 are boys.

 

[fluffycrow]

Agreed, all cockerels

 

[Short Round]

Thanks everyone for your replies. Appreciate it