CPU/GPU intensive Apps and high screen brightness (often encountered when using the iPad outdoors or in very bright ambient lighting conditions) can rapidly drain the iPad's battery. As the battery ages - and loses capacity relative to when it was new - the reduction in battery autonomy can become quite noticeable.
Speaking of personal experience, my own iPad Pro can deplete its battery at about 20-25% per hour when being used in such conditions.
If you continue to experience difficulties, you might need seek assistance directly from Apple Support - and request a remote diagnostic test of your iPad. You can contact the Support Team using the Support link at top-right or bottom-left of this page. Alternatively, you can initiate and manage your support cases using the excellent Apple Support App. If not already installed on your iPad, the App can be downloaded from the App Store:
https://apps.apple.com/gb/app/apple-support/id1130498044
You might also visit the Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) - where the technicians will be able to hands-on test and assess your iPad. Perhaps, since last tested, battery health will now be below the 80% threshold required to qualify for battery replacement under your AppleCare+ plan:
Genius Bar Reservation and Apple Support Options - Apple