Battery health drops to 95%

Perfectly normal. Expect Battery Health to decline an average of about 1% a month.

That's an average. Some months it might not decline at all, then drop 2% the following month.

Replace the battery when it is down to 80%

Batteries degrade over time with usage due to chemical aging, that's just how they work.

You can expect about a 1% drop per month with average use on an iPhone. This is an approximation, that is why it may be plus or minus a few percent on a month to month basis.

Apple recommends replacing it when it reaches 80%.

iPhone Battery Replacement.

iPhone Battery Service - Apple Support

About Lithium Ion Batteries

iPhone battery and performance - Apple Support (IN)

Here are some tips on maximizing battery life.

Batteries - Maximizing Performance - Apple

You're welcome.