arguing piggies

Question
Hello! so, heres my story, we started off with a lovely girl guinea pig called Buttercup. We got her a friend, another girl called Blossom. They immediately got on with each other and loved each others company. After a couple of weeks we found that the petshop had sold us a pregnant guinea pig. We got through that stage fine, Blossom had 2 girls and a boy (patch, the boy, and bubbles and stripe the girls) . When the time came we separated the boy and got a bigger hutch for the girls to live in together as they all got on so well.
The babies are about 3 months old now and it looks like one of the baby girls (bubbles) is getting a bit cross with the others  she started to get a lil terratorial over the food bowl and i saw her have an arguement with her mum!There was the usual bum wiggling/runbling but also nipping and she was shaking like she was angry.
I know a little bit of a rumble is expected sumtimes but i found some little tiny cuts and bits of pulled out fur on buttercup and bubbles has a little cut on her ear (healing now)
I didnt see who did it but i took bubbles out and left her out for a couple of hours and noticed there were no fighting noises or arguing coming from the hutch.
Is this normal or does she need seperating, what could have made just her like that? ive had guinea pigs for years and ive never come across this b4!
sorry if i wrote too much i jus didnt wanna miss n e thing out that mite help!

Answer
Emma,
I want to thank you for being so detailed. It really helps me out to figure out what's exactly going on. It sounds like Bubbles is trying to be the alpha female. The nipping and the fur pulling is a sign of trying to be the dominant guinea pig. I wouldn't seperate them, instead I would observe and watch them very carefully. Bubbles is battling for dominace and it's actually normal. Here is some more information on dominance issues.
http://www.cavyspirit.com/sociallife.htm#Introductions