That's pretty typical of a few of my planes. They'll slow to the point the tail is no longer providing enough lift to carry the back of the plane, so it starts settling. Will literally stop in mid air (usually without dropping a wing) if you don't give it a little bump of down as it slows to this point. The fact you still have "up" trim on it though, that's puzzling. When mine are like this, they've generally had CG trimmed for a flat elevator.

Haven't got this far with the Phoenix Edge yet. It's still flying on suggested (way forward of tube/spar). -Al