aggressive behavior between rats

Question
Hi Sandra.  I got 2 new female Rex rats about a month ago and I love them.  One is White in color with a brown hood, while the other is pure brown.  Over the past week or so I have noticed that the brown one jumps on the white one a lot and pins her to the ground.  The brown one is smaller than the white one, so I don't know if she is trying to show that she isn't afraid or what, but occasionally the white one will let out a little squeak.  The White does it to the brown one too.  Are they just playing, or is this aggressive behavior?  Also, the last couple of days I have come home from work and the white rat has a lot of red around her eyes, and i have read that this can be caused by stress, so I got another cage and separated them, and when I came home from work yesterday she didn't have it anymore.  Could it be my brown rat being mean to her, and if so is there anything i can do to limit this aggressive behavior?  I'm pretty sure their cage is big enough for the two of them.  I got two deluxe cages from SuperPet that measure 24.5" l x 12.5" w x 24.5" high each and stacked them on top of each other and cut a hole in the bottom of one so that they have access to both of them, and they both utilize that access.  Thanks for the help Sandra.

Answer
Hi Mark

I like your ideas about putting two cages together.  I actually did that myself before. I had three cages I used for babies or for senior rats that had to be in a small cage if they could not move around much any longer.  I had found myself with 3 unused 12 X 24 cages, so I stacked them on top of each other and added some holes and some ladders and ended up with a nice roomy 3 story cage!

Anyhow, it sounds like the girls are just playing with each other. How are they now that you have them apart?