I agreeI'm pretty sure that "Pepper" is a young male, ring just coming in. The other one I'm not sure... you might want to have DNA done just in case.
It sounds like Kiwi had a molt, they molt if I remember correctly, once a year.Immature birds: Lack the black ring, pink collar, or blue tint on the back of the head. Juveniles also have a coral pink beak with a pale tip. The young reach their adult plumage after their second full molt - at about 3 years of age.