When ph of the runoff is lower than what goes in, it tells you that the medium itself has a lower ph than the runoff. I.e. soil ph may read 5 or 5.5.
It looks as if the plant is light colored due to this problem. At a low ph certain nutrients are not being absorbed well or lockout can also occur if you are adding in the wrong ratios.
The solution if you re-used your soil is to add dolomite lime next time. In the current run I would carefully measure what goes in and out for several cycles.
Soil grows swing through a ph range, up or down. Since your ph is low, I would recommend watering next time at 7.0 and seeing the result coming out. I would tweak that up to 7.5ph input if the runoff is still below 6.2 or so. I would not run water with a ph much higher than that unless things really go south. It is not that far out of whack and may be a buildup of nutrients at the bottom of the pots.
So think like this...if I put in 7 and it comes out 6 or more, I have a swing from 7 to 6, which is almost ideal. If it still comes out low, adjust input a bit. If it begins leveling out around 6.5 (runoff), stay there for a while.
In my soil input is 6.4 to.6.6 and runoff if there is any (organic grow) comes out around 6.8. My soil itself starts at about 6.5ph after cooking and before starting the run.
my ph to 9.0 did a flush and no change on the ph in the soil
