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These extenders are driving me mad!

I've got the following:
4010 plugged into router in office.
4020 - one at desktop pc (office) and one at xbox (living room)- both ethernet connection to the device.
4220 - wireless extender in living room

Everything was great until I got a new router and now everything has gone wrong!

My smart tv will no longer pick up the 4220 although it seems to be working. My phone will connect to it but with a speed of 19mbps. If I'm right next to the router and my phone is connected to wifi directly rather than through TP link, then it's 50mbps.
Both 4020s are now only getting 19mbps and that's through a wired connection! My PC is next to my router so if I take off the 4020 and just connect directly wireless to the router, it's again much faster.

Why are the TP Links suddenly slowing down so much, and what can I do to fix it?

Any help is very much appreciated!!!