My plant leaves seem to be drying up and dying in random locations. I am in week 4. This grown in an indoor grow tent. My ppm level is about 320, and my ph is about 5.9. It is grown under a 450 watt led light. I thought maybe it was light burn, so I moved the light from 12in away to about 18in away. However, the problem is persisting. The temperature is a bit low at 65 degrees, and I am unsure of the humidity levels.