Yes Your right. You should read your water before you add nutes 200 PPM and over is hard water and needs nutes for hard water. If you use RO or distilled water I can tell you it's vary low in PPM's. I'm not familar with bluelab. Can you calibrate it ? It may need it. You and your plants are doing the right thing. No signs of over or under feeding is good. I would check the meter. I have a Hana now That reads EC , PPT and PH. PPT is PPM in the thousands. I can read as low as 10 PPM to 10 thousand PPT. Let us know what it is or if you need more help. I can tell you what mine are in both PPM and EC later when my light comes on. Show use a pic if you can.