are my guinea pigs fighting?

Question
Hi. Im annie, I just recently bought a guinea pig about 2 days ago, i named her pumpkin, she's about 8 weeks old, and when I brought her home, I seen that she wasnt being active, seemed very lonely. So I decided to go back to the pet store that I purchased her from, and buy her sister. [she had 2 sisters she was with, I am certain they were from the same breed] anyways, I bought ginger, and when i brought her home and put her in the cage along with pumpkin, I noticed pumpkin was sniffing her behind and light biting her behind. gingers teeth chatted and ran away. I have a little hide home in the cage for them.  pumpkin likes to hide in there, and whenever ginger gets near, she does a head bob with her, kinda nugding her face, and ginger runs away. when they are both out, trying to eat. they make squeaking sounds, and pumpkin continues to chase ginger, i am worried they are fighting. it doesnt seem intense, but i do not know if this is normal. before i bought them. they were both in the same cage with another sibling [female] and seemed to get along just fine. i do not know why they wouldnt in at my home, they grew up together. do you think i should seperate them? I just dont want things to get worse. i am worried, i love them both. is this aggressive behavior or is it normal? please help. thank you so much
*annie*

Answer
Pumpkin is showing her dominance over ginger which is normal GP behavior. She is also being territorial.
A little trick i have learnt is to put Vicks vapo rub cream on the nose and rump of both GP's to deter the behavior. The smell puts them off.

If they were biting each other and drawing blood then i would call it fighting
Guinea pigs will show you when they are about to fight by rearing their heads and showing their teeth and then lunging.

Clean out the cage with pet disinfectant and re introduce them on neutral territory in a run with plenty of veg and no hiding place and see if they sort themselves out. The hiding place seems to be causing a problem too which i have dealt with before myself. You can re introduce it once they have sorted their differences.