To Bee or Not to Bee?

Last year we brought on two hives from a very reputable leader in the bee-biz, Old Sol Enterprises.  They were new hives, fresh and strong.  Over the past year, we've seen one hive appearing much weaker than the other, and we can't seem to pinpoint why exactly.

We live across the street from a very large blueberry farm and just up stream of the Applegate River. It is beautiful where we live but I'm sure our bees are visiting our neighbors and I'm sure that any chemicals they are using will eventually make it back to our bee hives, and down the pristine Applegate River.  While I have no idea what pesticides they are using, I know they do spray as I see the workers out today in the fields spraying something.  We have lots of berry bushes along our property, a small vineyard and 6 fruit trees, a large garden and have planted lavender and plants that bees love, however, a bee will travel in a 3-mile radius and collect nectar and pollen from many sources.  While I know we are helping to raise healthy bees in a non-chemical environment, I know we can't protect them.