i don't wash my down unless it REALLY needs it... non of my quilts have been washed ... my JRB Hudson river is 4 years old and has seen lots of use never been washed and still has all it's loft ... another thing that can kill a quilt is the way you store it ... i found oversized bags are ok but i still would pull mine out and let them lay out for a week here or there... now i just hang then in the basement from the rafters
i found laying them on top of each other is no good as well.. best way is to let them hang

i think what i'm getting at is wash your down only if you really need to
and store it so it can loft ...

what soap did you use? and did you run a cycle of just water before you put your down in... sometimes soap can still be in the machine ... it's always good if your not sure to run a cycle before you put your down in ...
also did you use low temp to dry your down? too hot can also damage your quilts from what i was told