Any ideas? this is only showing on a few of the plants in the room, I don't think it's a cal-mag issue, but i may have been a little over zealous with the Mg in this batch of nutes so could this be toxicity?
Hmmm, I hope you are wrong, I'll have to see how it progresses. If it is, I have no idea how it got into my room, the mothers are all healthy, i sterilise everything between cuts when cloning and my room is very clean and air tight also, my media is brand new (canna coco). Apart from the discolouration, growth seems to be fine and they seem happy.