Trouble with numbers

The Downtown IPA is done. If I got anywhere near 100% efficiency it would have turned out to be an Imperial IPA with an OG around 1.090. But, I didn't and so it's a run of the mill IPA. Just kidding, this beer is gonna have some serious kick to it, and with 68% efficiency, I got a 1.063 OG which will still produce a pretty big beer. 4 ounces of hops in the boil and one waiting to be dry hopped. Mmm mmm. Can't wait

My last two batches have produced less than stellar efficiency. I got 65% for the pilsener and 68% today with the IPA. I'm not complaining about the numbers here, anything above 65% is considered good in homebrewing. What I am concerned about is the drop in efficiency. In my first three batches I got an average of 76% and then all of a sudden it drops to 65%. I think I may have narrowed it down to one of two factors. I didn't add gypsum to either of the last two batches, and they both also got stuck during sparging. I think if the grain were crushed a little less fine, and I added gypsum during the mash, my efficiency would go back up to the 70's. I'll have to wait until next time to find out. Darn, that means I get to brew again