hmm, I am running GH nutrients at 400 ppm.
I was previously running them on 100 ppm but since people told me I had a cal problem I added the 300 extra to the "recomended" 7ml/10L from GH themself.
I also flushed the system before with GH florakleen.
I just did a calibration on my PH meter (wich is new and came with fabric calibration) and it turns out it showed 0.6 PH to much... so all this time I have had my water at around 5.4 PH.
Could this be the problem?