Greetings everyone! Today I went to brew a Bell's Official clone and ended up quite under my target. Last time I brewed this recipe I had SG at 1.053. This time I have SG at 1.041(checked with refractometer, double checked and verified with a hydrometer). The grain bill is 5 lbs Pilsner, 5 lbs white wheat malt, and 1 lb flaked oats. I do BIAB. Both times I milled the grains as I was heating up the water for the mash(Strike water was 157 degrees, mash was at 150 degrees at start, 145 degrees after 90 minutes). Used 7 gallons of RO water total with 4g Calcium Chloride and 7g Gypsum. I mash with 5 gallons of water(90 minutes), drain with some squeezing for 30-60 minutes, then do a sparge with the remaining 2 gallons of water, drain for 20-30 minutes with some squeezing, then hang the bag over the kettle for the entire boil(1 hour). So my question is what went wrong with my process? I didn't weigh the bags of grain, just assumed they were correct(two-5 lb bags and a 1 lb bag) and milled(could the measurements have been off?). This was my tenth batch since I started milling my own grains(the other brews had no problem, could my mill be getting loose? I just checked and a credit card barely goes through, it catches the rollers on both sides). Anyways this one confused the heck out of me and was hoping for some advice. Thanks!