I would leave it alone... if the beer is fermenting, it isn't too cold! Lager yeast+cold ferment= clean beer/good lager. This should be an excellent beer.
45ish is my SOP ferm temp for lagers and have actually gone as low as 35 once, stepping down slowly over a week or so, and still had active ferment. The beer was amazing... it took a long time to ferment at that temp, but that was kind of the point.