PharmaCan,

Thank you for your informative post. I will be sure to keep the ph around 5.6-5.7 from now on.

The HPS is right around 30 inches (76cm) from the planting medium and about 20-22 inches (53cm) from the top of the leaves. Does the light need to be raised? I can raise it another 6.5 inches (16.5cm) easily using the chain but I could get another 3-4 inches (9cm) if I needed to.

As far as nutes go, is 1/4 strength in reference to the recommended dosage on the bottles or is that referring to a total of about 1300, divided by 4?

My tap water has a base of around 420 ppm, so I have a total of around 270 ppm of nutes in it. According to Diagnosing Marijuana Cannabis Plant Abuse Problems Charts and Photos
water with over 200 ppm starting out is too hard (too much Ca) which can lead to a mg def. My starting water is 400+, so I need to lower it somehow. Referencing onlinepot.org again, it says that using 1/4 teaspoon of epsom salt per gallon of water will reduce the lockout. What do you think?

Again, I really appreciate the help