Hi to all OG,
I have a RDWC setup in a tent and my tap water is 0.9 EC. Being it is DWC it doesnt leave much for everything else the plant needs. I have been through a fair bit to sort out my water issue and am finally there. My next grow should be fine but I am finishing off the current grow still which has evidence of issues from earlier in the grow. What i found working with my 0.9 EC water was that i could give the plant close to what it needed during veg as well as flower if i watch and adjust the system closely. However, it seems to be during the transition from veg into flower I am not able to give the plant all it needs. I guess as the plant starts requiring flower nutrients as well as calcium, magnesium and nitrogen as it is still stretching and growing in size. During the 4 weeks from switch to 2 weeks into flower the larger older leaves at the top of the plant, maybe 4th of the large leaves down f rom the top of each branch (each branch has bud sites and nodes/leaves much further down than that) start to yellow off. I still got great results out of the grows but I am still curious to find out what it would have been even though I should not have this trouble anymore. In the photo below you can see the larger leaves at the bottom/foreground of the photo. They are yellowing between the veins but the veins are still dark. The purpling on the petioles is genetics in this case even though the plant is deficient in something. I have grown another strain in here in the same system and exactly the same issue. My guess is either potassium or calcium deficiency leaning towards potassium but would love to hear some others opinions: