Has there been any mention of what HOPS are being utilized or the hop schedule???
Could be your water! Could be the pH of the finished beer.
Water or water chemistry might be pertenant to this discussion. Just call me crazy!
Seasonal water source changes in your area really need to be examined.
If it is totally across all varieties, ruling out bad choices of hop combinations, its probably the water, not your technique, since you have been brewing long enough not to need a lecture on techniques.
With the drought, water sources can change frequently.
Good luck!
I would review BeerSmith Podcast #70 on water. Colin does make reference to the final pH of the beer and its effects on it.
Just send a sample to Ward Labs.