My Female Rats Are Fighting

[JenaJupiter]

Hello, my name is Jena and I have two medium sized female rats who are fighting. I know play-fighting and tiffs for asserting dominance is common with rats but I am worried one may be bulling the other more and I don't know what to do. The rat in question is ending up with wounds and scabs on her body and she is a bit skinnier than her sister.
I just want to know if there is anything I should do to help reduce the fighting/wounds.

 

[jorats]

I would do a mite treatment with revolution. And then I would observe them again.