Battery health going down to 97% from a 100% in a week after updating to Tahoe

I don't really care about battery health but it seems weird that for 9 months the batt stayed at 100% and now it went down 3% in a week. Also the battery life is much worse with Tahoe then it was with Sonoma. My laptop has less than 70 cycles and was never fully discharged. Did the battery just recalibrate or is it a software related issue?