Over watered?
I'm no.expert but it does look like over watering. Which yes should be nearly impossible in Coco but I think it still can be done. And it's possible that the flow to each station might not be 100% even and this one could be getting a bit extra. The biggest issue I have with auto watering Coco is getting the same volume of feed to each plant.Shouldn't be. 70/30 coco perlite mix prob be hard to. They all 3 been getting same fertigation for past 10 days