I don't know what went wrong with your batch, but just out of curiosity can you describe the off flavor? I know almost every one on here say never heat, but I just get an musty funk every time I try, So I tried another home brewers mead and theirs had that same funk. I don't know what it is, but I went back to heating. May be just lazy, but I am happy with my mead, so that's all that really matters.