Hello Kate! I have four rabbits and had the same problem but slightly different. I had two bonded males, then a few months later got a female then another female. My boys, Fred and George, LOVED her at first sight. They were grooming and cuddling and were totally fine with her being there. But Ginny, the other female HATED her. She didn’t want her to be there at all and any time she saw her she would growl, bite, pull fur, lunge, everything to scare and hurt her. I started only one on one bonding sessions with those two and whenever Ginny started lunging at the new female (Hermione) I would gently hold her back until she stopped squirming, give both of them a little treat and go again and again until Ginny realized she only got the treat when she was calm and nice. Of course, this only worked while I was with them so I put peanut butter on top of Hermione’s head because Ginny loves it and finally got her to start grooming her like that.
I think what really did it was moving cages. I got a new giant cage from a friend that would fit all four and put Hermione in there first. She stayed in there for about a day until the whole thing smelled completely like her (she likes to chin things). I let the boys in next and they were totally fine with the place belonging to her. They settled right in, no litter box accidents or anything. THEN I let Ginny in. She only smell she didn’t smell there was her own so she knew it wasn’t only her territory, it was Hermione’s and she had to share it with her. After that there were hardly any problems bonding and now they’re besties, inseparable.
So maybe a cage switch would work? I know it’s rpetty expensive so maybe instead of buying a totally new cage you could wash the one you have really well until there are no rabbit smells there at all and do what I did. Or move the location of the cage?
Hope this helps!

Hi, if you only picked them up last week it is too early to start bonding. Your new girls need at least a week to settle in, then 4 weeks of pre bonding. That’s when you do things like switch their litter trays and toys, or switch their cages. This way they can get used to each others scents without physical contact. Once you have done pre bonding for 4 or more weeks then it’s actual bonding time. bonding should be done in neutral territory, just starting with short sessions.

I recently bonded four bunnies. My journal is called “what do you call four bonded bunnies?” If you want to check it out. However my bonding was a bit odd. One of my boys gets aggressive when nervous so I actually had to do the bond in the room they were to live in because he knew that room and felt safe. Even though that room was anything but neutral territory!

Are all your buns spayed/neutered?

Oh, and until they are fully bonded don’t let them be able to reach each other at night. They can night each others faces through play pen bars. I would perhaps set up an additional barrier to prevent any physical biting opportunities

Really? A week? I didn’t do that at all! :/ Hermione was NEVER really injured (the most she got was a cuff to the ear or maybe a growl from Ginny) and she got to see them every day from literally the day I got her. I find this has usually been better rather than them getting used to the idea that they will be alone at the house and then as soon as they’re settled they’re thrown into meeting new rabbits.
I forget how long it took for them to be fully bonded and ready to move in together but it was something like two to three weeks, maybe a month. Ginny took a little longer, I kept her away from Hermione and the boys, switching them between cages until she was fully okay with her, that was maybe a month and a week or so. I have never seen rabbits with a stronger bond than mine (not to brag or anything, it’s just true). Ginny is with Hermione wherever she goes in the house, following her and running toward her when she gets scared because Hermione is bigger than her now. I haven’t had a SINGLE problem between them since they all moved in together and they don’t bite, chase, growl or lunge, ever.
I guess all rabbits are different and the bonding process takes longer but it’s never taken more than a few weeks for me.