Internet download Speed is Poor

I have a same problem.

I have a Roku streaming+ stick as well as chrome cast on the same TV. 

Roku network check shows at most 1-3Mbps on 5G network while Chrome cast can stream HD quality without any issue.

Internet speed test on my 5G with my smart phone keeps showing 80-90Mbps even farther away from the router than the Roku stick. 

All other devices (Windows laptop, applie macbook, three smart phones) are streaming HD quality without any buffering.

I tried to power off the stick five minutes and reset the device too.

It didn't help.

I need help from Roku support!!! 

I did so many things, so I don't know what helped, but what was funny is that I don't think I unplugged my Roku express after I reset my wifi range extender--you'd think that would be one of the first things I'd do. So in case that was what fixed it, thanks for the suggestion.

here's my case, in case it helps someone:
My problem started after I purposely left my Motorola modem and Netgear wi-fi range extender unplugged overnight. When I turned everything back on, my wireless network wasn't showing up at all on my devices (only the extender, which wasn't connecting). I only had internet access through my computer's wired connection, so I reset the extender and the modem/router, and that fixed everything EXCEPT THE ROKU--all my other wireless devices were working as before, but the Roku showed Excellent signal strength and ZERO download speed with the extender (The Roku did connect and work decently with the main modem, however, but the signal was weak). Just now, I was fiddling some more with the extender and the Roku, turning them on and off and checking for updates. The last thing I did was to reboot my extender and attempt to update the firmware (which is another pain because I could only do it on the iPad, and I lost connection while I was doing that, and now I can't log back in to verify that it was successful, GRRR NETGEAR!), and before checking to see if that worked, I read this post, unplugged the ROKU, and plugged it back in, and for now, the ROKU is recognizing both the modem and the extender, and I'm able to use the ROKU as before.