Just a suggestion but try a product called Rescue Remedy which you put in their drinking water. I know others have had success with it helping to calm everyone down so they can get along. Also, I use Felliway Spray and Plug Ins to help calm my neutered male who decided to start spraying my new carpet and painted wall. I think the new stuff in the house was the final straw. He was already stressed from adding our third cat to the house a couple months earlier. You can buy these products at most pet stores. I got Feliway at PetsMart.

Good luck!