CocoCola said:

I learned much of what I know from Canna Nutrients. Here's an excerpt from their growing guide and it has been my personal experience that around week 2 - 4 you start seeing drops in pH.

"During the growing phase, plants tend to cause the nutrient solution’s pH to rise. This happens because at this stage the roots can excrete relative large quantities of elements that increase the pH. During the flowering phase,the reverse happens: the roots now produce acidic secretions causing the nutrient solution’s pH to fall."

Source: http://www.cannagardening.com/everything_about_ec_ph_and_ppm_using_aqua

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MurderVille said:

Great article, really good information.

One thing I noticed in the article was that it mentioned how the nutrient solution plays a part in root secretions.

"To a large extent, the nutrient solution’s composition determines whether or not the roots excrete predominantly alkaline or acidic secretions."

If I were a betting man, this distinction may be the difference between solutions with organics and without them.

For example, while using Sensi, I noticed how solutions in flower would drop in ph like this article discussed (and this would drive me nuts), whereas with mineral based solutions without organics, the ph would still raise in flower.

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