Why?

[Gavinthechickenman]

So I have three sapphire gems two roosters and one Pullet they are all 5 months old the Pullet and one rooster are growing and maturing perfectly but the other rooster isn’t he is the same size as the Pullet he still has small pink crown and wattles he eats and drinks fine but why is he so behind

 

[Gavinthechickenman]

This is him

 

[Gavinthechickenman]

And this is his brother