Battery health down issue on my iPhone

What problem? You need to describe what the issue is if you want help.

Batteries degrade over time with usage due to chemical aging.

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%. To check your battery health, go to Settings > Battery > Battery Health.

iPhone Battery Replacement.

iPhone Battery Replacement - 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 have not described what the problem is. The battery health is supposed to go down and it would be a problem if it did not.