Toof Decay - 3rd Grow

Despite my training efforts and increased lighting (150W HPS + 2x 55W Autocob), the plants are still stretching like crazy. They've more than doubled in the last week and are growing 1-2" a day. The tallest plant is almost 2 feet tall and not showing any signs of stopping. My tent is only 5' tall and the lights are as high as they can go so I ordered a new 2'x4' tent that is 6'7" tall, which should help considerably. My light schedule has been 17/7 since the second or third week. In hindsight, I should have gone with something closer to 20/4, but didn't anticipate this much stretching and am hoping it's almost over. With all the growth, the plants have been super thirsty and are drinking about a gallon every other day. The N toxicity I was seeing appears to have resolved itself after I did a flush with FoxFarm Sledgehammer last weekend. The runoff pH was a little on the low side (6.0) and run off ppm was on the high side (one plant was 2000ppm), but I only did 1.25 gal, rather than 2-3x the pot size as some people recommend. Sledgehammer seems to do a great job without needing as much water. Overall I'm happy with the progress, but I wish they would stop stretching and put more effort into the bud sites. I've cut back on the nitrogen by reducing the amount of Mega Crop and no longer using CalMag+. I'm also adding some Bud Explosion and Sweet Candy. I'm hoping this encourages the plants to focus more energy on flowering.