I was dubious as to the value of the Controller App when I first changed from running the Controller Software on a client's desktop pc to an OC200. I've only just twigged the significance of the Up arrows in blue circles that were showing against each of the listed APs on my smartphone - I now realise that meant an upgrade was available.

In the app, on the top menu bar you can click on the white outlined up arrow key, to do a batch firmware upgrade. That seemed to work for 5 of the APs but not for the rest. So I did them manually by clicking on each AP and scrolling to the bottom of the screen where there was 'Firmware Upgrade' with a red dot adjacent. Click that line and job started, quickly moved on to the others - for a short while showing as 'upgrading' and a few minutes later all done.

Even if the batch upgrade didn't quite work, the job for 25 APs was quickly done from the comfort of my off-site armchair :-)