Battery degraded to 82% in 1 month

The 90 day warranty on repairs and repair parts would likely cover it if it dips below the magic 80% battery health. However, this sounds really unusual. Nothing short of leaving it continuously at high heat is likely to cause anything like that. Even if you used and charged the battery 24/7, that would be less than 100 cycles and I would imagine no worse than 95%.

With something that unusual, you might try seeing if they consider it a bad battery - especially if the diagnostics show something unusual.

Hello,

according to Apple, a healthy lithium-ion battery should take about 300-500 charge cycles to reach around 80% battery health. So assuming you haven’t charged it from 0%-100% 300 times, I assume that it is not normal and you may have gotten a bad battery.

Make an appointment at take it back. It's covered by at least a 90 day warranty.