I agree with Cugin - get another light - Make sure you spent the little extra on a ballast that will take both MH and SPS bulbs... I have to put out major this summer to get a 1,000 watt that goes both ways. I screwed up and bought 3 400 watts that only run HPS - Spose to have those MH lamps for vegging...
Fill your water jugs at least 48 hours in advance to let the clorine drop - also keep the water out of the light.
Get a digital ph meter if you have the mo. I mix the ph levels in a 5 gal. bucket before watering.
Good luck