Seth, I wouldn't be horrified by those measurments... They are within the acceptable, normal range, IMO. Granted, they are on the low end of acceptable...
I would dose enough of Randy's Mg suppliment to raise Mg 100 points and increase my CA reactor output (for me this means droping the pH in my CA reactor .05 units for you it may be increasing the CA reactor efflient flow rate) and re-test in a couple days.