Today I just brewed for the first time since moving to DC from CO...it was not a happy brew day
My efficency went from about 75% down to 55%!!!
My strike temp made my mash about 6 degrees warmer than usual (160 instead of 154). It took me about 15 min to recover. Did that kill my eff?
I did everything else the same. Except I didn't use iodine to test for conversion...I just waited my usual hour.
What was your mash thickness and grain bill? Did you leave it for an hour after stabilizing the temps, or just 45 minutes longer? By getting the grains to 160* you denatured a lot of the enzymes. There would still be enough left to finish conversion, but it would take some extra time, maybe even longer than 60 minutes. That right there could be your whole problem.
It could also be just a few small errors in measurments (temps which could effect hydrometer readings, larger volume than usual) that added up to make your efficeincy appear lower. Hell, if it's your first time brewing in a new place, it could even be that your process was a little different, which sent you screwey.