Quote Originally Posted by MimbresValley
"if the ppms are rising and ph dropping you are feeding to much. as the plants drink the water there is more nutes in it and the ph buffers are then lowering your ph as the water lvl drops.
it will be the exact opposite if you feed to low. your ppms will lower and your ph will rise."
Further clarification

These are not the only two options by the way, for instance you can have ppms rising and ph going up as well, which could be because of the water, or the nutrients you are using causing the ph to go up.

Like if you have root problems(pythium,etc.), your ph will generally go down regardless of what the EC/PPM is, brown algae will cause your ph to go up.
So there isnt just one set of rules, as there are lots of variables that come into play.:rastasmoke: