Review on Hydroponics & Aquarium PPM and pH Meter Kit - Water Quality Tester for Pools Included by Clayton Jimenez

I have only used this product 3 times in the last 6 months to measure the pH of pool water. There was a serious problem today when the meter gave an incorrect reading of the buffer solution used to calibrate the meter. The gauge has drifted for the past week as a range of pH readings trended lower. I tested with standard buffer solution. The meter cannot display the pH value of the buffer. I bought this pH meter 8 months ago, can I return it?