As iPad doesn't have a Battery Health feature, how did you establish the maximum battery capacity?
If you are experiencing difficulties, or have any concerns, you might be best advised to seek assistance directly from Apple Support - who can run remote diagnostic tests if needed. 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 from Apple devices using the excellent Apple Support App. If not already installed, the App can be downloaded from the App Store:
https://apps.apple.com/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 test and assess your iPad:
Genius Bar Reservation and Apple Support Options - Apple