I probably have around 45 or 50 AG batches under my belt at this point, so I consider myself a pretty seasoned brewer. Tonight a brewed an IPA, and for the first time ever got a significantly low efficiency. I normally get in the range of 75% to 78%, but I got 60%. Every other number I had control over, I nailed. My mash temp was spot on, my sparge was the same as always (I fly sparge), my pre-boil volume was right on, and my post boil volume was only about a 1/2 quart high. The only thing that I can come up with is that my LHBS crushed my grain improperly. I plan to ask them if they made any changes to their mill the next time I'm there. Is there any other possible problem that I'm overlooking?