Hello,
I also only had 1 of the 3 needing the update. But that was using DJI fly app.
To be 100% sure, I connected my
Ma2 to my computer.
Using DJI assistant 2 under Windows : I had to update battery 2 and 3. (battery 1 was updated using DJI fly, firmware confirmed Ok using DJI assistant2)
Yous should check all your batteries with DJI assistant !