The microbes in the medium can change the pH in the medium. So it's impossible to answer your question. The pH going in will not always be the pH of the runoff.
How do you know if you have nute lockout? From the ppm In the runoff?
@chriscovey Just posted some examples below in a reply to mwhite's reply
Lock out can be caused by both ppm and pH. If your plant shows deficiency the ppm will say if by not enough in soil or to much, with the ph most all nutrients are absorbed at different ph levels, going to high or two low can lock out nutrients once you passed their threshold.
to add to this, here are some examples (using synthetic nutrients)...
1. Your pH is within the ideal range but the PPM is over 2000 and your plant is showing deficiencies. This is probably a lockout due to salt buildup.
2. Your PPM is in the ideal range but your pH is 7.5 and your plant is showing deficiencies. This is probably a lockout due to pH being too high.
3. Your PPM is in the ideal range but your pH is 5.1 and your plant is showing deficiencies. This is probably a lockout due to pH being too low.
a good soil ph meter would make your life so much easier. you cant trust runoff ph too much in my opinion .
works very very good . (tried a few) :)