All good points @aart. Behaviors, feeding and disease are different depending on age.
Sometimes I'll go to answer a question when someone asks about their chicks, only to find out later they have 2 year old birds. Or they ask about their hens when the birds are actually a week old. They may be...
It is normal but depending on how many pullets/hens you have, it may not be a problem. You could confine him to his own quarters for another month or two.