For the record, have been testing nutrient profiles for the past 2 years now. You can most definatly over feed your plants.....Ratios are EVERYTHING!!! If anything you want to forget PPM's and target a good ratio, your EC will fall into place. Once we stopped going by PPM's and started going by ratios and developing a nutrient profile, it was like magic how all the problems went away (including PH) and plants grew healthier and faster than ever before!!
Peace~!