Battery Health related issues

This is completely normal behavior for a battery. Batteries are degradable products that wear with every charging cycle. Dropping of battery health is normal, and not a thing to worry about, when it drops under the 80% you can get your battery changed. It took my phone more then 4 years to drop to 80% It looks like it is going fast, but that is very relative

See this link to an user tip I Wrote where I explain more about battery health

About battery health on your iPhone - Apple Community

Batteries are CONSUMABLE components and the maximum capacity will eventually become less as the battery ages. There's no need to worry.

Apple provides battery replacement service for free if your device's maximum battery capacity gets below 80% within one year.