My Marzen finished fermenting at 1.013 and the sample had a butterscotch aftertaste which I attributed to diacetyl. I slowly raised the temperature from 50 to 62 and after a few days I still detected butterscotch. I raised it again to 68 and let it sit a few more days and I'm still getting butterscotch. How long does it typically take for the diacetyl to clear up? I thought a day or 2, but my samples tell me otherwise. I also detected some harsher flavors in this last sample. Is 68 too high a temp for a diacetyl rest with a lager yeast? I used WLP820 and it tasted very clean in the first 2 samples. Thanks.