Kitten biting other cats..not play

I have a 13 week old kitten (a rescue who I bottlefed from 1 week old) and she has recently started doing something odd. She will go up to some of the other kittens (fosters as well as my own cat) and sniff them vigorously and then grab a hold of some of their skin and bite down hard. She prefers to do it to their heads. I know she is not playing, I am very experienced with cat play and have seen her play. She just grabs as much skin on their heads as possible and bites it as hard as she can until they yelp and jerk away. Any ideas on what she may be doing?

Are there any adult cats that can keep her in line? In my experience when a kitten starts acting wacky like that it's often an adult cat that gives them a swipe and a hiss to get back in line

That does sound bizarre, but remember as much as we all love the bottle babies, kittens that are not raised by a momma cat can have odd behaviors.