Yep. Just because Dallas was the first does not necessarily mean he will remain the alpha dog. The dogs have to work it out and sometimes the new comer ends being the alpha dog. That happened to a freind of mine and oddly enough her older one was a male and new comer was a female. I don;t know if this is true or not but I've heard that female's can actually be more dominating then the males. Who knows. It probably just depends on the dog not it s*x
My Belle would bark, growl and snap at Cinnamon a lot in the beginning but she never actually bit her or anything. At times they end up going at it and Belle's growls so load i swear she will hurt Cinnamon but I've put my hand into the mix of the wrestling match and I've found that they play nibble with each other just like they do with me.
Oh my gosh. Its so fun to watch them play now. They have a blast and its like a tornado coming through at times, especially when all 3 are in the mix.
You probably just need to give it time.
I was a little nervous with how things would work out at first too.
You just want to make sure that you never allow them to actually hurt one another. They will need supervised time together for a long time.