iPad losing power

Hi there,
Iā€™m running touchable pro on 12.9ā€ iPad Pro (2nd gen with lightning cable).
When I use live, even with a fast charge cable plugged into :computer: , the battery in the iPad slowly drains. Without the cable it drains a whole lot faster.
I have tried a few different cables and same problem.
Has anyone else had this problem?
Running iOS 15.0.2
No other programs running and in aeroplane mode.
Thanks