Splitting dogs up in the same home where there are unresolved issues is not a wise idea because this prevents the dogs from ever resolving the isssue and, if they come into contact again, they'll carry on where they left off. It's not really a viable option and any pet behaviourist would probably advise against it.

The problem seems to be that the pecking order is not stable between the female dogs and this is what they are trying to sort out.
Sometimes, the way the human owners treat the dogs can create more confusion and, in turn, more aggression in order to try and create a stable heirachy.

There is one female who is obviously not interested in climbing the ladder or is too submissive to want to try. It's the others really that things need to change more with.
You need to decide who is naturally the most doominant and has the advantage over the others and then who comes second, then third. You might need to watch the dogs for a few days to see how they act around each other generally. The signs are often very subtle so look carefully.

Once you've found out the order they presently seem to be in even though it sounds like things are a little too evenly matched and are probably made more unstable by the inconsistent way in which they are treated by the humans of the house, you need to emphasize this by treating them as such. no. 1 gets fed first, fussed first, groomed first, even let off and put on lead first when walked and generally treated as higher thanking than no. 2 by yourselves. This must involve every person in the house. Obviously, they need to know you are boss although this dominance thing between owners and dogs is being abandoned by behaviourists as rubbish, the dogs still need to know you aren't the push over type so they are more likely to respect your decision on who is higher ranking amongst them.
No. 2 will be fed, fussed, put on lead, taken off lead, groomed, everything you do with them before no. 3 and if you fuss one and a lower one tries to push in for attention, the lower one should be ignored because this is a more subtle way of trying to climb the ladder, it is not about jealousy. The more attention you can command, the more dominant you are in other words. If one dog can steal the attention of an individual away from another, that dog has won the test of who deserves that individuals attention the most.

You must stick rigidly to these new rules because the dogs won't forget and will notice if you slip up.
I had to do this when my two bitches went through a bad patch years ago and they stopped fighting and I never had a problem since and I could leave them alone together fine without issues.