have a 6 pack hydro system going, bottom leaves of the plants have suddenly appeared to die. They are very very dry and crumble to the touch. Also have some strange white/yellow streaking that has appeared on a few of the plants. My PH was FUBAR yesterday (shot up to 8.1 for some reason) and I did a water change. I change the water at least once a week. Nutrient mix is pretty tame...600 watt light was about 12 inches from the tops of the plants...PH is good today 5.7, Dont know what other details to add, other than I am a beginner, this is my first time growing. I hope I added all the details you guys need to tell me what might be happening.