Battery health problem why 87% battery health in 10 months

Batteries degrade over time with usage, that's just how they work. You can expect about a 1% drop per month with average use on an iPhone.

Apple recommends replacing it when it reaches 80%

Here are some tips on maximizing battery life.

https://www.apple.com/batteries/maximizing-performance/

You don't have a problem yet,

When it gets to 79% have an Apple repair shop fit a new battery.