Aquarium PH Adjuster and Test Kit

Is Aquarium PH Adjuster ok to use to adjust PH levels in my water that i give my plants? I have an Aquarium Pharmaceuticals API PH test kit. Im not familiar with PH test kits but this one i add 3 drops of a solution provided with the kit into 5ml of water n mix it together. The water changes color and i match the color to a color chart. Are these types of kits acurate? Any help would be great. Thanks
 
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