Can anybody tell me what went wrong with this mash bill? I used 8 ga of water 12 lbs of flaked corn, 4lbs Briess malted barley, & 2lbs wheat flake all run through my Monster mill. I boiled at 256 deg for an hour in a 15 ga Blichman kettle using a commercial agitator. I then brought down to 90 deg with a chiller and poured into two 5ga ferment buckets and pitched a champaign yeast called LALVIN D47. Initial Brix was 15.5 and after 4 days only went down to 10 Brix - I guess yielding only 5.5%abv.
What'd I do wrong?