My low EC + 40% Power of my Sanlight lead to yellowing of the leafs - after raising to EC 1.2+ problem was fixed. In hindsight i raised the EC too slowly which i'll fix for the next run.
At this point in time my watering was fully automated using a Fritz DECT200 - this was managed by a python script on my Home NAS Raspi - i made the script publicly available here https://github.com/heyjan/fritzbox_water_automation
Watering schedule was 9 shots in total for 60 seconds each