Battery voltage and percentage values drifting

[Ortwin]

I have noticed that the battery voltage and percentage on my two 9.5 KW batteries have drifted over the past two to 3 weeks on the app. The mv difference used to be around 3 to 8 but today I noticed it on one was at 150mv difference. Also the cell percentages which one was down to 70% has now dropped to 63%.
I wonder if this is due to the way octopus energy ate controlling my solar system.

[RubikCube]

Could be due to a change in usage pattern that it is showing different values.

Could also be that the battery is ageing. Voltage spread is likely to increase with age, and the performance percentages are likely to fall.