Queen's Pawn Game Opening Question

I hope I got this in the right forum...

As of lately I have tried to do 1.d4 openings in my Correspondance Games.  I notice that when I do, my rating will almost bottom out due to the losses that I go through.   
Now I know that with my win/loss rate and my rating that my game needs more improvement than just my opening skills.  So I am definetely not trying to avoid maybe issues that I have in the middle game, end game, pawn structure etc.  I also realize that many issues may also be dependent on how the opponent's skill level is as well.

Just for discussion sake, what could be a possible reason that my ability to win decreases drastically when I play 1.d4.  Could it be from the lack of ability to play closed tactical positions and I would be better in the open positions or maybe something else that I am not realizing? 

Switching first moves changes everything about the nature of the ensuing game, so I'm not surprised you're having trouble. At least part of the problem would be having to relearn everything: plans, unit placement, traps, openings, relative pace of the game, etc. It could also have to do with your middlegame play, but my bet would be on my first guess: unfamiliarity with a totally new terrain.