Dog, I have a red lense filter on the Halogen and I used a homemade spectrometer and could not find any blue light coming through. To answer your question, no I do not use blue light on the dark side of the "martian method". But a sidenote...At the begining of flower, I use shitloads of blue leds and filterless halogen, along with the procyon during the light period. For the dark I use the red halogen.
As far as the nute uptake, I had a similar problem, then I used a bone meal tea and some epsom salt cause I was getting nute lockout. Dont know if that is related to your prob.

GL HF!