Sorry to hear this. The male is usually the smaller of the pair. Sometimes its just hard to figure out why they perish. I have no idea what a "typical" life span of a clownfish is, but you have to be doing something right for a six year run.
I had a male /female (non-reproductive) pair for about 12 years. The smaller male died of unknown causes that I could detect (clear eyes, no fungus, no labored breathing, all normal signs to me). I thought the female may go shortly thereafter. She is now 20 and I wouldn't even try to bring in another clown as I'm sure it would just be killed. I keep on thinking that the female looks a bit ragged as she now frequently has some split fins etc. but she hangs in there. If you are transferring to a new tank an addition is possible. Good Luck!