PH Swings?

[Goud S!]

I recently started a new grow using my Autopot system and have 8 plants in various stages that appear to be doing faaairly well.. I have an issue with two of the purple lemonades... They are in the 1st row of pots closest to the inlet from the reservoir. 2 of the 3 in that row are showing discoloration of Brown spots and yellowing leaves which started in middle and are working their way up. The ph in the valve chamber came up at 6.2 while the ph in the main reservoir was at 6.01. I also checked the ph in the very last row of the line in the last valve chamber and it shows 6.36. I understand there will be variances and the like but my real question comes with the major swings I am seeing in the main reservoir pretty much daily. I have been adjusting the ph down almost every single evening since I noticed the issue with the purple lemonades.. Last night I came home and the ph was at 6.18 I dropped in some PH down and brought it to 5.52.. This evening I came home to find the ph at 6.01 And again adjusted it back down to 5.58. Those are the 2 most recent but I have been adjusting all along. I see no sludge or any particulate matter floating in the reservoir and I sterilized the system with bleach and 30% peroxide (separately of course) prior to reactivating it for this grow. I am using Cana Coco A and B as well as bulletproof , Cal Mag and I just with this reservoir change added some PK1314. The last time I had huge ph swings like this, the continuous use of a

submersible pump was the culprit because it was overoxygenating the tank and causing unwanted growth. I could really use some advice if anybody has any. Thanks for reading if you made it this far! Sorry for the crappy pics.