Battery health reduced from 100 to 93 before 6 months

No, you're not. Batteries are consumable parts and battery health will continue to decline with each full cycle charge. This is normal and has happened with every smart phone you've ever owned. You just didn't have a battery health monitor to show you. If your battery health declines below 80% in in the first twelve months it would be considered a warranty issue, but that is highly unlikely.

In the meantime, read this link about how to ensure you are charging your phone the best way to preserve battery health --> iPhone Battery and Performance - Apple Support