If you haven't already I'd suggest reading through whiskyscience.blogspot here's a link with a breakdown of what flavours are created when why and by what.
http://whiskyscience.blogspot.com/2011/ ... s.html?m=1I don't profess to have all the answers especially as I haven't smelt or tasted your sample bit there's a lot more at play than just the grain.
Both of the yeasts are known for high ester formation and if the balance of pitch rate temp aeration of wort length of time between pitching and closing off the oxygen ie lid isn't right then the result can become unbalanced, usually this settles with more time on oak.
Was the wash temp controlled if not what was the day time temp on the first 2 or 3 days?