iPhone 13 mini battery degradation

Hi I bought a refurbished iPhone 13 mini around 2 months ago being completely assured that it only has the original Apple components. When I bought it the battery’s health was at 97% maximum capacity, however over the past 2 months of use it has dropped down to 92%. Within the last month I’ve even followed the suggestions that apple has given to slow the rate of degradation, but this has not served much purpose as it has continued to decline and the same rate (about 1% per week). Is there something that is wrong with my phone software that is causing it to run things when it shouldn’t be , have I simply been using it too much or could it be something to do with the internal software?

If someone could get back to me ASAP that would be great, thanks😊.

Cheers,

Flynn Steinhoff