Well, what a turnaround. I did discover in the end I had a light leak which was behind all of the problems I was having. So the plants obviously were on the verge of dying (I included some pics below of what they looked like 4 weeks ago). They look healthy now and the roots (albeit with nutrient stains) look healthy. pH levels are 6.0. The brown stuff is cinnamon to repel the gnats... lest they even TRY to come close. But here is the zinger. One TDS meter shows 950ppm (normal I think) The other TDS/EC shows 4200ppm AND 8800 EC (off the charts if it is accurate... I am going to recalibrate it to check....) There is definitely sediment at the bottom of the reservoir which I believe is salt buildup. At this point what would your diagnoses and advice be? Maybe flush and lay off the nutrients for a few days? Or flush and refeed? Thanks This is how they looked 4 weeks ago...
I changed (and cleaned) the res last night and made up some new juice. The EC pen said 1200 last night but today it read 1850 (!) wtf. There must have been an air bubble under the EC sensor last night. I replaced 4L of solution (of the 24L total) with 4L RO + 4ml calimag. Brought the solution down to 1650. I will let it ride till tomorrow and see if it rises or drops and go from there. How old is your solution? I change mine out usually about every 10 days or so. I normally take some bleach water and wipe down the res before I replace the solution.
Probably a month now... it's time... I'm pretty certain it's the residue build-up.. you can probably even see it in the pic...