I have ipad air 3 too
Have yu experienced a little fast battery drain on yr air 3 recently too ??
Can it also occur cos of 30w apple fast charger that i use ??
I mean it sure charges my ipad really fast but maybe my ipad battery is draining a bit quick due to it ??
My Air 3 is still giving me over a week of battery life on a charge unless I use it heavily (iOS 13). But I'm a light user (mostly reading, data input via bluetooth keyboard to Day One, etc...).
Charging fast / slow shouldn't affect drain rate. The iPad will accept only a safe charge so you could have a 200w charger and it would only pull what it wants. I'd start looking at your Settings --> Battery to see what apps are taking power - consider doing a hard reset (Power + Home button), etc.
New iOS usually means less than average battery life for the first few days.