Purple Slow Growth

Getting pretty slow growth with droopy leaves and purple stems, especially on the top side of the leaf stems. I think the problem is either temp issues or ph. They're in bcuzz soil-less mix ([FONT=Arial, Helvetica, sans-serif]70% Sphagnum Peat, 30% coarse perlite[/FONT][FONT=Arial, Helvetica, sans-serif] I believe) I believe this medium requires ph closers to hydro levels right? I started at around 5.9, but recently increased the ph to 6.1 after what appeared to be some lockout issues. [/FONT]Now I'm noticing lots of purples and some droopy leaves right after watering..

Another possibility is temp issues. Looks like a high of 75F and a low of 45F. Do I need to add a heater @ night? Would 45F cause droopy leaves, purple, and slow growth? Thanks!

Cold nights in comparision with the day temp will cause leaves to purple and can stunt growth. Although hybrids also can purple at the end of the cycle, and the buds also do aswell. Though its probably because of the cold, its a hard factor to change.