Basket,
They first had a natural decline. It seems to every sheep herd, at least from what I've noticed... they hit their "peak" years, then the quality falls off a bit. In the 90's a guy could kill a 195 ram in there without even trying. By 2005, B&C rams were tough to come by.
Then, yeah, in the last couple years there's been a couple pneumonia outbreaks in different parts of the area...