What type of growing medium are you using?Going to hps for flower from MH has been the standard for 20 years or so, however, there is some debate whether the extra growth is due to the redder spectrum, or the simple fact that a 400 w HPS puts out almost double the lumens than a 400 watt MH light does. So changing out the MH for an HPS will give your plants far more lumens, and should increase growth. Years ago I did it all with a MH light with good results. As far as stretching, to me it seems more variety induced. I have run MH/HPS and have now moved on to full spectrum leds and I find my plants stretch for the first 3 weeks or so of flower and then stop, some varieties stretch more than others. Some say cooler nights help stretching, my room drops to 64F, so I am not sure if that is what does it or not. You can also raise the light a bit to encourage stretching.
Here's a pix of my plants at the flip, and 8 weeks later at harvest. They are under 700 watts, @ 46 watts a sq. foot.
I use Sunshine #4 peat. Advanced Nutrients had a handbook and was extolling the benefits of their nutes using #4 and I have had great success with it. I currently use Emerald Harvest since the ph perfect Sensi line had been temporarily pulled in Canada. Check out my journals in my signature if you want to know more!
