For vegging PH should be lower, 5.8 being optimal (good job Avon:thumbsup but anywhere between 5.5 and 6.0. In flowering you should let your Start higher like 6.2 but not over 6.5. The reasoning behind this is if your system is dialed in correctly when vegging with healthy plants your PH is going to drift up. When flowering your PH will drift down. By starting your PH in the correct area you will prevent stressing the plants by shocking them with sudden PH changes. For instance, You fill your rez with fresh water, nutes and whatever else your throwing in. PH is right where you want it at 5.8. You go to bed and get up late in the morning and dont have time to check plants but wtf they be alright :thumbsup:. You go to work and when you return at the end of your day the first thing you want to do is visit the ladies, why not thats what I do . You trip over the dog, kiss the cat and kick the wife to make it to the grow room to find ot ....... SHIT my PH is 6.1!!!!!!! You grab your PH down, liquid or powder no matter, or whatever organic you use and dose it till your PH reads 5.7!! Good job right down where your suppose to be but what did that .4 do to the plants. Everyone and their brother preaches DO NOT STRESS YOUR PLANTS!!! If a tiny bit of light makes it through a zipper your plants can hermie while flowering but what is that light in fact but stress in a round about way.

:angry3: Ok I'm done preaching. I stand behind what I wrote. I vote against PH. If you are in a climate where you are using a heater you need to face it away from the plants. Heat the room not the plants. Also the fan being to close at to high of a speed can effect the way a plant looks.
Cannabis Plant and Pest Problem Solver - Pictorial - 420 Magazine That is from a different site but is the best pictorial problem solver that I have found so far.