How do pH changes spread?

[Tomatoesonly]

Kind of an odd question, but how do you think pH changes you make, spread when not every drop touches another drop so that their is some kind of alteration to the pH?
Imagine you add some lower pH solution to a bottom fed plant. Do the changes only spread upward as it takes in nutrients, in effect you will have a pH striated pot of media? Do the changes spread like an electrical current, so that when a pH change is added it flows out like charged ions until an equilibrium is achieved?
How many areas of a system could have vastly different pH values?

 

[Creeperpark]

Molecules link up by magnetic attraction from a positive or negative charge. Hydrogen being the transporter will exchange nutrients based on + or - charge. As the hydrogen diminishes the pH will be dominated by hydroxyl ions making the pH stable. If a liquid has a charge then the charge will spread until the hydrogen is gone. If there is no charge there will be no movement.