They went from a pair to a trio, and doing that has messed up your girls bond. Youll have to keep them all completely separate for about two months. Each in their own cages and not free roaming together. The more you allow them to be together, the more they fight, the less likely it is that they will be able to bond again after the two month split. After this two month break, youll have to try bonding them in a neutral territory (a room theyve never been). Start short and often (2 minutes, pet everyone, put them back in their own cages; repeat an hour later). Youll do this for a few days then progress to longer times together. Youll keep progressing how long they stay together based on how well to get along the previous session. After there are NO fights or signs of aggression, move them to the pen and cage they will be sharing. Again, start short and often and slowly progress to longer sessions until everyone is completely comfortable with one another
Please note that not all rabbits will get along with one another. If after a few months of bonding (after the two month break) they just arnt getting along, dont try to force it. It will only cause more problems