Hello, I have a first edition apple watch updated to last OS. I am using it after some months not using it a lot. I wake up at 7:30, dont do any workout, and at 22:00 battery is 10% so goes to that saveing battery special mode. I remember when i buyed it at 223:00 or 23:00 battery was still 20% or 25%. Is the problem the OS? or using it two years?