Please don't be so hard on yourself. I have 9 males and 4 females and have not had the spraying problem (yet) so don't blame yourself. Has Harper been spraying the entire time that you've had the 2 new ones? Was your moving at the same time as the 2 new ones? Could it have been the feral foster baby that was temporarily at your house? Could he be marking a place that the former owners of the house may not have cleaned up properly? I have heard MANY favorable reports about Feliway. Do you have any females that are not spayed (I am sure you don't ) but I had a neutered male long ago who would spray when she was in heat. and I only had 4 cats then