Dreytek Wi-Fi woes

[cheekymeerkat]

We use a Dreytek 2860 series router, which centrally manages an AP810, and has done for many years now. So far so good.
However, we recently installed 2 x Amazon Firesticks and they make the wifi choppy, I've isolated the issue to the fire sticks because when they're plugged in and the CCTV app is on, I get packet loss on my Android phone when connected to the same wifi, and our Windows Mobile wifi hand held terminals all have packet loss too which can frustrate the pickers because they can't do their job quickly.

I should note that the Firesticks are used to receive IP Camera streams (the camera's themselves are hard wired), and use ONVIF standards.
We use them as viewing monitor's. I've noted that each firestick receives a constantly 10mbps when we have the app on (streaming 4 cameras per firestick). Now with just one firestick on, it's usually OK, but with two firesticks, it's impossible to use the wifi - but the firesticks seem to have no packet loss because the video is always live!
For them moment, we've had to turn them off completely because the wifi was becoming too unstable.

Can anyone explain why?
I do have a spare AP810 so I'm thinking of making a separate network just for the fire sticks - what do you think?

Thanks...