Potential Tragedy

I am not going to be of any help, as I would have no idea what to do.  I just wanted to give you some support.  Hang in there.  I was teared up just reading this. 

It sounds to me like they have not sorted out their pack order yet. Unfortunately I don't know how to solve this other than just letting them fight it out which is obviously not an option right now. No treats or food when they're together would definitely be a good idea, but you can't tell other members of the pack what their ranks are even if you are leader, it's something they have to sort out. Interfering by taking treats away from one and giving to another will probably only prolong the uncertainty. Hopefully someone else will have more practical suggestions for you.

although training will help, managing the situation so that the dogs are never together is necessary.  You have two issues that are impacting the situation.  Littermates who are more bonded and therefore often react more intensely because they feed off each other  and  bitch on bitch aggression.  The living space and time out of restricted areas will be have to be scheduled and monitored.
 
Rehoming could work and I would suggest one of the Rotts. Practiced aggression can often results in more aggression in the future.  No matter how careful you are, there are going to be mistakes and dogs will be together.
 
Rehoming can be a loving choice where you place a dog in a situation in which someone else can offer a better quality of life compared to the current situation.

mrv,  I think you hit it on the head.  But there's another factor at play here: Deafness.  If the two Rotties have picked up on the deafness of the dalmation then they may see that as a weakness.  In the pack there is no room for weakness, lest the "hunt" be compromised.  In a tightly bonded pack sometimes a wounded animal or an older animal will be nursed and treated as a puppy, but in a loosely bonded pack the dog will be cast out and met with aggression whenever it tries to re-enter the pack area. 
 
IMO one of these dogs needs to be rehomed, or if that is not an option, the trio mustn't be allowed together at any time.  The violence will continue until one of them is either gone or not living. 

Practiced aggression can often results in more aggression in the future.

 
Unfortunately, I can tell you firsthand that this is absolutely true.  In addition, the fights will be more difficult to stop if allowed to continue.  I have 2 females (labs) and they have had serious fights.  We manage them separately and I only allow them to be together if my husband is home.  He allows them to be together if he's alone with them, but he's much stronger than me.  In our situation, things have gotten better.  The last fight was in Sept and prior to that it had been several months.  Initially though, it was every few weeks until we started keeping them separated and watching them carefully for triggers.  We feed them separately (they can't even see each other eat), we never give them treats together either.  It is difficult though and would be impossible for us with 3 dogs. 
I honestly think that as hard as it might be to imagine, rehoming one of the dogs would be best. I'd seek a consult with a behaviorist and get some advice on which one it should be.  That sounds horrible, but you don't want to go thru the pain or rehoming one and then still have battles between the remaining 2.
I'm sorry you're going thru this.  I really do empathize.

My heart aches for Sapphire, I'm sorry for what your going through.

Are your Rotties spayed and neutered?  If not, please do so ASAP. 
 
You will need to keep them separated and managing dogs like that is difficult and time consuming.  I fyou don't you will probably end up with a dead dalmation.  I have a dog that I have to "manage".  If I were you'd I'd rehome one of them, preferably the female.
 
Have you given thought to signing these dogs (and yourself) up for obedience classes?  Books and videos are great but going to a class is really important and you need help. 

I agree if they arent fixed do so immediatly. Hopefully someone can come and help you but IMO the best thing to do would be to rehome one of the dogs. My heart goes out to Saphire. I have a deaf Dalmatian also, and I know she would never ever recover if she wasnt with me anymore. It is a lot harder for a deaf dog to readjust. (Not to mention how hard it is to rehome a deaf dog).
 
I also know that it is true, my "pack" knows that Marley is deaf and I have seen a couple of my fosters & my other dal (who is the alpha) gang up on her. It made me really angry at the other dogs (they wernt aggressive, just playing, I thought it was very unfair of them), but Marley handles herself well. She lets them know when she isnt playing and they respect her. It was never aggressive, but I am a very protective mom of Marley (more than my other dogs) & it makes me mad to see the other dogs pick on her because she is deaf. However, it is just a fact of life. It bothered me at first but if you think about it it is instinct, I dont know how but they realize she is deaf and in the wild the deaf dogs wouldnt last very long.

I think all three dogs are female. If I were in this situation, I would consider rehoming one of the Rotties, Just for the fact that their littermates and you trying to manage them might be an uphill battle. Is your bf willing to help?

I agree w/ mrv, and one of the rotties is a male and one a female, you need to rehome the female,  and do it quickly,  you really need to protect Sapphire, she's counting on you.

Thanks so much to everyone who took the time to respond to my last post re: my Rotts attacking my deaf Dalmation. Yes, all three dogs are female and the Rotts are not spayed. We have made that a priority next to keeping Sapphire safe.
Hopefully this will be the miracle I'm praying for to avoid rehoming one of my precious Rotts. Now I know how Meryl Streep felt in "Sophie's Choice" when she delivered the famous line, "Nehmen Sie das Madchen."[]
 
Rainbow

Spaying is a good step, but you'll never be able to let your guard down.  Good luck!

Good luck with your decision.  I hope the spaying works.  I have been close to being in your position. 
I just would warn that rehoming a dog that bites for any reason, including another dog, could be a problem.           

You need the help of a good trainer/behaviorist.  What the others have told you is true.  It is never a good idea to adopt littermates, and this is probably contributing to the problem.  To manage multiple dogs in a household, it is safest if all the dogs regard  you as the leader.  When you adopt siblings, unfortunately, they tend to rely on each other more than on the humans. 
You must keep your Dal safe from the other two.  Dogs that go for the neck and draw blood are serious most of the time, so she is in danger of, as you put it, a "potential tragedy".  Then, you would not only have a dead dog, you would *not* then be able to rehome the aggressor - even Rott rescue groups don't take kindly to rehoming a dog that has killed another dog or sunk teeth into human flesh.  Please, take this very, very seriously.  You need to spay the females asap, enroll in some classes, read Patricia McConnell's book "Feeling Outnumbered? How to Manage and Enjoy Your Multi-Dog Household", and get an appointment with a behaviorist that is well recommended.  Mic on this board can help you find one if you PM him.