Absolutely not, if it's the factory mainspring. Unless you or someone else cut the mainspring, and I mean by more than a couple coils, it's not that. The mainspring is designed to last many tens of thousands of rounds, and is quite a bit more powerful than it needs to be.
Anyway, you might have issues with your firing pin safety. I would recommend going to a knowledgable smith, or calling Kimber.
Of course, it could always be ammo related too. I just had two misfires in a row on a reliable gun where the hammer dropped all the way. It was a Springfield with no mechanical issues or a firing pin safety. Neither primer had an indentation, and the gun was in perfect mechanical shape.
I had the same happen with a Glock during a class. Of about 500 rounds fired, I probably had 70 failure to fires. It was all bad primers in brand new LE Federal ammo.