Cutting off large fan and shade leaves is going to hurt your plant not help it. Plants need all their leaves to produce the maximum amount of chlorophyll and food. Removing leaves slows chlorophyll production, stresses the plant and stunts growth. Remove only dead leaves that are more than 50% damaged. Remove spindly branches and growth that is not collecting light energy, including dead and dying leaves. It is OK to prune the lower 1/3 of your plant to improve air flow and to keep pests, fungus and mildew off of your plants. Root rot fungi cause roots to turn from a healthy white to light brown. As the rot progresses, roots turn dark brown. Leaf chlorosis is followed by wilting of the older leaves on the entire plant, and its growth slows. When sever, rot progresses up to the base of the plant stock, turning it dark. Root rot is most common when roots are deprived of oxygen and stand in un-aerated water, it has nothing to do with the rez temp. The AG is designed to keep the rez between 70-80 degrees. The roots need warmth to grow. Rez temps are critical with DWC but not the AG. The key to preventing and controlling it is cleanliness. Use fresh, sterile medium and clean the rez when changing nutes. Make sure calcium levels are adequate and do not over fertilize with nitrogen. Keep pH levels at 5.8-6 to lower disease occurrence. If you added the air pump and air stone to your rez and keep your pH at 5.8-6 you will not have a problem with root rot again. You can also use Binab, Bio-Fungus, RootSheild, Supresivit, Trichopel, H2O2 to treat it. You can add H2O2 with your nutes if you are using regular non-organic hydroponic nutes to treat and keep the rot under contol. Do Not add H2O2 to your nutes if you are using organic nutes like Foxfarm and SubCulture because it will kill the good microbials. If you are using organics only flush with the H2O2 and pH adjusted water. Buy some General Hydrponics Ph up and down to control the pH or you can use fish aquarium pH and down from the pet store. I check my pH every morning and top off the rez if it needs it with pH adjusted water. I also have a air stone in each of my rez. By doing this i have never had a problem with root rot in my AG's. All i do is check the pH every day and change the nutes on schedule and my plants do very well. I hope this helps.