Battery health decreasing

Hi, i brought a Xs max few days ago with 100% battery health. I checked by 3utools also. After that I brought a new Baseus 20W cable to charge the phone fast. But after using it about 3 days my battery health decreases 100% to 93%. I don’t know where is the problem. My battery charging cycle count is only 15 times. How can anyones phone is going 100% to 93% with only 15 times charge. Please give me a solution what am I doing now?

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