iPad updating slowly with OctoPi?

Has anyone had a problem where iOS devices via Safari update slowly? During a print the iPads on my network degrade and only update every 3-12 seconds after a few minutes or so. Video from the camera stutters crazily. Two iMacs on the same network, one wired and one wireless update relentlessly perfectly every second during a print. On the iOS devices I have tried putting them within feet of the wireless router, no luck - they still only update every few seconds. I have cleared their cache and reset their network settings. Doing a speedtest the iMacs and the iOS devices have similar speeds with only the iOS devices having a ping time of a few more ms than the iMacs. Surely this is something the dunderheads at Apple have done. Any ideas on how to work around this?

EDIT: Figured it out - the problem was the wifi connection on the Raspberry Pi was weak. When the Pi is hardwired with an ethernet cable Safari in iOS goes at full speed. Why the iMacs ran fine but iPads didn't is still a mystery.