This may help you more than I could since you know best what your entire scenario is. I dont remember where I got this so I cant give credit where its due, but this is a pretty good basic guide that should help to keep most out of trouble with their plants and res values.
If you are dealing with multiple individual reservoirs, you better get good
Water Level EC/PPM pH Reading
Static Static Static - Plant not feeding/drinking, change EC, check meters. Usually, lowering the EC a little should get the plant feeding again
Static Static Rising - Ph buffers probably raising ph. This is usual. Having a static water level is not though, so again, a slight reduction in EC or a res change should resolve this.
Static Static Falling - Usual cause of this is when media has been rinsed at a lower ph than you require. The other possibility is that too much CO2 has been pumped into the water. See Note 1.Change your res and look at the volume of air pumped plus look at your air source.
Static Rising Static - Plant is leeching nutrition, raise EC. Note 2
Static Rising Rising- Plant leeching nutrition, Raise EC. An unusual state. The rising ph is probably caused by what nutrient leeching back. If these are alkaline, it will lead to the rise in ph. Could also be ph buffers.
Static Rising Falling - As above but be aware of the acid rain effect mentioned in note 1. Res change, plus increase in EC.
Static Falling Static - Plant eating but not drinking. Not ideal. Lower EC or res change
Static Falling Rising - As above but rising ph is a better sign. Lower EC slightly or res change.
Static Falling Falling- Falling ph along with falling EC but no drop in water level suggests a res change. Could also be an acid rain effect as per note 1. Depending on other symptoms, lowering EC after res change.
Falling Static Static- Perfect conditions. EC and ph are at the correct level.
Falling Static Rising- Normal state most people encounter. Nothing to worry about, carry on doing what you are doing unless other plant symptoms.
Falling Static Falling- Res change plus a change of EC. Lower EC if over 1.4, raise EC if lower than 1.0
Falling Rising Static- Plant is drinking more than eating, lower EC.
Falling Rising Rising- Plant is drinking more than eating, lower EC
Falling Rising Falling- Plant is drinking more than eating, lower EC. Also, res change due to possible acid rain problem.
Falling Falling Static- Hungry plant, raise EC. Very good situation to be in. Nute buffers are working and plant is taking a balance of nutrients.
Falling Falling Rising- Almost as above, usually considered almost perfect, raise EC slightly.
Falling Falling Falling- Res change. Potential acid rain issue but plant is still eating & drinking. Raise EC on new res.
