You want your PH to be lower, you can literally use Lemon Juice or Lime Juice to bring it down for now but you will need to check your PH after adjusting. I would recommend ordering the bellow products they are super cheap and super super effective. Literally I use a few drops to bring my 20 gallon reservoir from 6.2 PH down to 5.8.. Literally maybe 1 ML per 20 gallons of water to adjust.
Amazon.com: CYCO pH Down 500 mL (12/Cs) : Patio, Lawn & Garden
www.amazon.com
If you want a cheap PH test it would be something like this:
https://www.amazon.com/General-Hydroponics-pH-Control-Kit/dp/B000BNKWZY
for all 3 products your looking at 40 bucks. You should only need PH down from the sound of it though. The liquid tester is super reliable and very accurate, avoid cheap PH pens for the life of you. For PH pen I recommend nothing but Blue Labs but they are not cheap...
The Digital PH pens on Amazon/eBay that cost $20-30 are always out of calibration and can cost you your yield and quality.
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