why do i have normal upload and latency but very slow download speed suddenly

Previously was working well. Not sure what i changed. I did temporarily open a guest network with airport extreme but have since closed it. Not sure if that goes with the timing of this. I have multiple devices in my home with airport extreme, 6th gen? Previously my xbox 360 worked in my bedroom as a media console to stream plex. one day it had to buffer and buffer and now is unwatchable. latency and upload are great. but download is 0.5 mbps. this is the issue and i assume in the settings of the airport extreme. all other devices working without a hitch. I know there is no bandwidth limiter, but maybe port settings? static ip? what could suddenly do this. the xbox is basically right by the router. going to run a cable to see if its hardware on the xbox but its in a different room and this is not ideal long term...and also seems unlikely. thanks in advance.