Chickens haven't hit puberty

[samj4ms]

We've had three Silkie chickens that haven't hit puberty like AT ALL. We've had them for probably 6 months now and they're still chirping just like chicks and haven't displayed any signs of puberty at all. Their siblings from the same clutch have already hit puberty so I don't think it's a genetic thing. We have had issues with chicken lice and worms which might be the cause but we've been managing them well and none of the silkies experiencing this are underweight. Can someone explain this?

 

[nuthatched]

Where'd you get them?
Diet?
Are they feathering normal?
How are you treating the parasites?

 

[sourland]

The parasites may have delayed maturation, but most likely they are just genetically programmed to be slower maturing than their siblings.