problem after adding third dog

Question
Hello!  I'm at my witt's end with a problem with my dogs.  I've had Clover, a beagle/boxer mix, since she was 8 wks, and she is now 7.  Two years ago we got another 8 wk puppy, Izzy, (lab mix) after our bulldog (Ophie) passed away.  Then, about 8 months ago I found a little 7 wk mutt puppy running down the highway and brought her home.  She's Peanut, now 8months old.
Here's the thing, Clover has always had a dominant streak with other dogs, but was always FINE with Izzy.  For 2 years they lived in harmony.  Then Peanut came along, and things were fine until Peanut got to be bigger than both of them.  Everyone gets along with Peanut fine, but CLOVER AND IZZY have started fighting everyday!  Clover usually starts the fight, but ALWAYS gets hurt the most because she's small.  She is quite obedient, even does "tricks," but I don't know how to stop her from starting these fights and getting hurt.  By the way, Izzy is typically very submissive and is typically afraid of everything, but once Clover attacks her of course she goes in to fight mode to defend herself.  I can't let Clover keep getting hurt!  What can I do??

Answer
Hi Heather.
Sorry to hear you are having problems.  With the severity of this behaviour problem I think you need to consult a behaviourist asap.  The problems are arising because Izzy hasnow reached an age where she would be challenging for the title of alpha female in the wild and Clover is trying to keep her own authority established up there.  With packs of female dogs living in one house this is a fairly common problem.  I dont know if you have already done so but I would have Izzy neutered asap if she is still entire and get peanut done while you're at it to try and prevent a problem occuring with her when she reaches the same age.
Keep the dogs separate for now, you will have to try and work with a professional on establishing a dominance order for them so they live in relative harmony.  Without observing the dogs in person I cannot tell you which dog would be the natural alpha dog to advise you on a plan of action (and often it is not the dog you might think at first).
It may or may not be possible to re-establish harmony between them and the behaviourist may recommend re-homing one of the dogs which is obviously not what you want but could be in their best interests in the long run.
You might wish to invest in muzzles for them for the short term so you can be sure they will not hurt each other any more while you are sorting the problem out.
Best of luck, I hope this has helped a little.
Sarah