First time grower here. My leaves are turning a whitish color on the tips. Also, The stalks on the plants have purple veins. I am using soil,GH nutes, 400 watt MH, in a 2x4 tent. My tent is in my basement and the temp gets down to 62 degrees when the lights off, and up to 80 with the light on. I cant find much info on the purple veins so its hard to find the cause. any help would be appreciated.