I've had several batches of Mr. BEER come out short on abv by a few percent. I try to follow the directions religiously but some batches just come up very short. Most recently American lager, came out 3.57% after 16 days at 64-66°. I've had a suspicion that this is a yeast problem. I can see the yeast getting blown out by some if the high malt recipes but this one? I'm thinking old yeast. I brewed it within a week of receiving. Idk what do you guys think? Do you activate your yeast first?