From what I understand/have experienced, if the clowns have been alone for too long they can turn into females so depending on if your new one was alone it could have already changed sex. Also, if you get two that are similar in size the fighting, I've found, is usually worse.
I made the mistake of getting two that were too close in size and neither would give up the dominance. There were never any major fights and they did sleep in the same LTA together but would squabble all day. Ended up just seperating them and finding a much smaller clown. The small one almost immediately did the "please don't kill me shuffle" and all has been right ever since.
HTH.