the other day i looked at them and the top was droping a bit then the next day it was turning yellow and then brown or dead but its only at the top of the plant. I water every 3 days about when soil is dry, temp is between 75 and 95 rarely 95 - 100, I fertelize everytime i water with 20-20-20. got a fan 5in in the room. with windows open. Could it be heat stress or is it a nute problem. light is about 2 feet away from plant 400 watt High Pressure Sodium. heat is from light only and room temp. thanks alot guys. My first grow.