I recently remade a recipe of mine from a few years ago. I didn't change much from back then, and still using roughly the same equipment. Only thing that changed so far is I moved into a new house, so the water supply is slightly different. We only moved across town, so I don't think water chemistry has much to do with it.
My results weren't much different than last time, pretty precise... But not accurate. (also the color this time appears much darker, but that isn't super concerning just yet). I bought the grain from NB already crushed because I don't own a mill yet.
My brew house efficiency is very low. If I plugged in all my fermentable ingredients into a computer program, and account for low efficiency, I still come in under the numbers. I feel like I'm hovering around 50% efficiency or worse. That is a very alarming number to me, but I don't know what area to focus on to improve those numbers. Water temperature was fine (154) , as was pH (strike was 5.6). No stuck mashes, vorlauf went smoothly. Gathered about 2.75 gallons of first runnings (did not test gravity of these), then batch sparged. I did a batch sparging method that worked for me in the past that took about a total of 35 minutes. I don't think I need to list the recipe here, but obviously I can if needed.
What could possibly have gone "wrong" here? Outside of getting a heated mash tun or a HERMS, I don't know what to change next time. But 50% or lower feels like failure to me, and that color darkness feels weird. I bet the beer tastes fine after all is said and done, but I feel like I'm throwing money away in the form of gravity points somewhere.