Its because of that hole next to the plant. Change your rez out and put a dixie cup in the hole. Use like a tsp of bleach for that rez and it should clean your roots up. But it will raise your pH so be wary. Start your pH around 6.4 on rez change to allow for the pH swing which should drop to 5.8 in about 4 to 5 days. Its better to set your Ph high then lower. Because if you set it 5.8 in four days it will drop to the low 5's in no time. Also throw a frozen 2 liter bottle in your rez before the lights come on to help your rez temps down.. are you using airstones?
