One's store bought and the other is one I breed but they've been together since they were two months old and no problems. (untill now) They're about a year in a halve now.
Sky the blue bully (that's her new nick name) is the one starting everything with baby Bajha. And I can't find a cause! They get the same food and attention and the cage is the same as allways. What's Sky's problem?!
Is the cage large enough for two? I have found once I increased my cage size Odin and Bastian stopped fighting.
Also, make sure it is the fighting that is causing this. I though my two rats fighting were causing their cuts but it turned out they had lice and I had to treat that. They still fight from time to time but aren't irritated as much since they have no lice anymore and have no cuts! Plus the cage is larger and that helps immensely <3
I haven't seen them exactly. I heard a lot of painfull sounding squeeks looked over and there box was bouncing around. I went over and took away the box to find a very fluffy and mad Sky and a very scared and jumpy Bajha. I took Bajha out and she was shake'in and squeeked pain squeekes when I pet her and she would cringe away somtimes.
There wounds are on the cheeks and neck and there shoulders and some farther down.
Is one of them more the aggressor? Was she always the alpha? Watch their behaviours carefully. If the aggressor just wants to be left alone and the other insists on being with her it sounds like she isn't feeling well. If the aggressor chases down the other girl, then it might be different. I would treat for mites anyways just in case, since you can do it cheaply with Ivermectin or pick up Revolution from your vet.
The cage is large enough for them to get away from each other? When did the fighting begin, has there been any changes in yours or their lives at that time?
Rats can be surprisingly sensitive. I helped a woman who moved and her rats got fearful and she thought they hated her. Many emails later and descriptions of their behaviours, and videos I sent to show her how I handle my own rats, she figured out she picked them up in a way they didn't like, plus they had moved and even though she had cats all along they went into prey mode since it was a new environment and she covered the bed (cat smell) like I suggested and they were happy confident girls again.
You're cage sounds the same size as mine was. I added a smaller cage to it with an additional hidey hole and this helps immensly. Also treating their mites will help more than you think. Odin's wounds looked like puncture wounds and I could of swore they were fight wounds but they were just really deep scratches or something as they went away after the Invetermicin treatment. I suggest getting them to the vet and taking care of their mites and possibly finding ways to increase their cage a tad.
Maybe they didn't do that in the past but rats grow up and change plus this could be different types of pest that are more irritating despite their lack in numbers. Good luck.