The THC light was about the same lightness, but the other two were darker. I am guessing that because the only thing I have in my system is THC is why that light was lighter. It just must be below the 50nl cutoff but still something there?

The line in the THC panel is almost always lighter than the other drug panels. There is no meaning attributed to the intensity of a line. Once again, a faint line is a negative.

Youre worrying yourself over nothing.