First Ever Poor Efficiency

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?

How long did your grain sit crushed before you brewed and was this a recipe you have done before? Id ask the guys if they changed grain supply or changed the grain crusher at all as well.. ive noticed a difference in brewing with grain just crushed and grain that sat for a day or two.

Assuming you have brewed this recipe before on that system, a change in ingredients seems most likely. Malt supplier, freshness, grind, or mismeasurement of weights could all be reasons.

If possible, take a look at your spent grains...a poor crush is perhaps even more apparent post mash IME. Look for larger more whole pieces of grain.