i now have 5 all-grain beers that i've brewed, and the first 3 were pretty much spot on where i wanted my gravities to be. but the last 2 have been way off. the only thing i remember switching in the process is my sink water filter. i used a brita filter on the first 3 batches, and switched to a pur filter for the last 2. my thermometer reads exactly 212 degrees when in boiling water, so i don't think that is the problem. i brewed last night mashed at 149 degrees, and after 90 minutes it only dropped to 148. the SG was supposed to be 1.071 and it ended up being 1.058. any ideas? could it be the pur water filter screwing up my water?