Hi Veg,
Little consolation that it is; a good friend of mine (a game keeper) warned me when I first started out on a large scale that "Where there's livestock there's dead stock". None of us like to loose bees but sometimes as the others have said, it's just not avoidable.
I myself have had an odd experience this year as it's the first time that I've ever had more colonies come through than I went into winter with....not STRICTLY true, I admit, but basically I had two nucs which had failed miserably to produce anything other than drone layers -in a perfect world they'd have have been liquidated last August but due to things out of my control they endded up being left in the yard to be moved away this year but they both now posses solid slabs of brood and are flying/collecting pollen well.
Best Wishes,
Roland