Yeah I have that GH ph kit as well. It is Hard to get an accurate reading of nutrient water and especially a runoff sample. You won't get accurate colors at all due to water being mixed. Like was stated by Lady the test drops used with pure clean water is not very accurate as it is. Time to bite the bullet and get a ph pen as well as reference solutions and cleaning storage fluid. I got one from Amazon, not the cheapest and not the best by any means but it has been used alongside a $1000 pro ph tester and is very accurate to the same readings.
So I personally can vouch for this pen Hi Tech Portable Accurate Digital Pen Type pH Meter (0.0-14.0 Range) BackLit Display 0.01 Resolution , ATC - 100% Warranty; Hydroponics, Aquarium, Bee Hi Tech Portable Accurate Digital Pen Type pH Meter (0.0-14.0 Range) BackLit Display 0.01 Resolution , ATC - 100% Warranty; Hydroponics, Aquarium, Beer Brewing, BONUS: FREE Calibration Powder Included
You will be able to eliminate any ph problems going forward for the rest of grows and gives you peace of mind knowing that ph is not a problem.
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