Purple Kush Auto

I tried to spot the cause of the yellowing leaves. I kept the ph between 6.2 - 6.8 and the ppm highest level been 1500 in the start of flower but now is 1100. Another grower told me about calmag but because of the ppm I have not added much nutrients. Is it too late to add it? I was planning to make a last feeding. Note: I checked under the pot and there was some dried roots, too much water? No water? Root bound? And this goes hand to hand with the yellowing leaves?