I'm using the ebb & grow 12 bucket system for the first time. I love the system's ease of use, but I'm getting concerned about my ppm's. Every time I do a water change, my ppm's shoot up from 1200 to 1900 after a few cycles (the 1200 reading is after all of my nutes are added). I clean out the res and fill bucket with every water change. Where are these extra ppm's coming from? Are they from the water that stays at the bottom of the 12 buckets? Has anyone else had this problem? Any suggestions or advice?