Run-Off pH Increase - Cause Unknown

[kingkola1]

I am growing in 1/3 Ocean Farm, 1/3 peralite, and 1/3 coco using 2-Part Emerald Harvest nutrients with reverse osmosis water (my tap water is extremely ‘hard’ with chlorine and chloromine’s). I water & feed drain to waste. I did a feeding in week 3 of flowering (day 55 from seed) and had a drain to waste run off pH of 6.5 which was within 0.5 pH from my 6.0 pH feeding solution. Okay, but it was near the edge of my limits so when I watered mid-week when the grow media was very dry using my usual Cal-Mag and RO water solution but pH adjusted down this time to 5.8. However, to my surprise the run off pH was at 7.0! So I checked my pH meter and the calibration is right on. It just doesn’t make sense to me unless the plants themselves are wildly changing the pH of the Grow media as they mature more in the flowering stage. Could that be true? I am trying to figure out why the run off came out so high so I can properly adjust my next watering or feeding pH. Any ideas?

[South Sierra Dude]

Ph ranges its not static. Stay the course. Anyways ph 6 not 5 before water/feed.

[Karlee]

Ph can change for lots of reasons and plant stress does for sure, temps wild, cold, I fed my plants last night at 6.00 PH and the run off was 6.3 today I had a little nute burn so I flushed the burned plant and that run off was 6.2
I agree with SSD go for 6.00 and then it can go a little up or down without stressing.

[kingkola1]

Thanks SSD and Karlee. This is my first grow so everything is new. Will stick with 6.0 in the future.