Really concerned about fighting

Question
I'm so sorry this is so long, but I want to be sure and give you all the information!

I have 2 female pugs (sisters from the same litter) that are about 15 months old. When they were little, they used to do the "play fighting" which we figured was just the alpha dominance thing, but over the last several months it's escalated into so much more than playing and they are full out fighting with each other almost daily - we're talking growling, gnawing at each others necks and faces, standing on their back feet swatting and biting at each other, and sometimes drawing blood! IT'S SO SCARY!!! Usually Sasha (the runt) starts it, then Sophie tries to defend herself, which then just makes Sasha even more mad and she starts it up again. And it's never really one particular thing that causes it - sometimes it'll start over a toy that one of them has, other times they'll be walking alongside each other and just start up.....just depends on the day! And when they get in that "mode", they don't hear a thing! We've tried yelling "NO", swatting them with newspaper, telling them to sit, you name it! We found the only way to really break it up is to each grab a dog, but we have to count to 3 and do simultaneous grabbing, otherwise you end up in the middle of it! And you can't do it alone! My poor husband tried separating them by himself the other day and now has 5 stitches in his finger to show for it! Plus, you have to take them to separate rooms or else they just stare and growl at each other and try to get out of our arms to start up again. We've also tried just letting them "work it out" but it seems like it just goes on forever and I'm really concerned that something more serious is going to happen one of these days! One thing I must mention though - they only do this with each other and get along great most of the time! They play, cuddle and sleep together and are sooooo sweet when they're not trying to tear each other apart!!! They are absolutely wonderful with people, kids, other animals, public places - you know, that general happiness that makes a pug a pug!  :0)  We are out of ideas on how to handle and/or prevent this so any ideas, tips or suggestions are greatly appreciated! Thank you!!!!

Answer
Littermates, especially of the same sex, often get into this trouble.  Temperament being so similar, it's quite difficult for them to establish rank.  Guarding food/water and other resources (such as toys) is often the first indication of a problem.  You need a credentialed behaviorist (not a dog trainer with make believe titles) to assess whether or not the relationship between these two can be successfully rehabilitated.  It may have gone too far and one may have to be rehomed.