4x Northern Lights #5 x Haze

The sprouts gained another pair of leaves during their first night under lights in the watering system. I let them have just plain water for a couple days and then gave 25ml of each Remo's nutrients. It's a lot less than what they advice on the charts, but the water EC is now at 0.6 so this is perfect for me. Just before I was about to add the first nutrients, I noticed the water EC was for some reason at 1.4 even though I never added anything. This was confusing to me especially because the tank was filled with about 50l of water so that means there had to be a substantial amount of something affecting the EC. I have no idea what had affected this. Only thing that I did that was irregular was that I had some other seedlings in the tank before this, but decided on the last minute that I'm not going to grow them and just took them out. Still no explanation why the EC had gone to such levels. I had cleaned the tank very carefully beforehand. I decided to drain the tank and fill it with pure tap water and then add the nutrients and PH balancer. I think this means I have to monitor the EC super carefully. I also had only the other light operating at minimum = 60watts and today I put the other light also on minimum, so thats 120watts of light. Im going to use the dimmer to add light daily or every other day just a little bit until they grow a little more. I have two large Co2 Exhale mushroom bags sitting on the pots, and i switch the pots they are on to give them equally the most direct Co2. Later I will add two alcohol brewing buckets to really boost the Co2 levels. I also buried the seedlings a bit more today to get the root game started most efficiently.