WiFi speeds are never guaranteed. There's a chance that there's nothing wrong but just that there's some kind of interference whether that's your neighbours WiFi or some other device or applicance causing you trouble.
If speed is a priority then a wired connection would always be preferable. But you could certainly try things like switching your router off and back on to see if it changes anything, as well as making sure the hub is unobstructed, ideally high off the ground, not shut into cupboards or hidden behidn TVs, and not near things like microwave ovens, cordless phones etc. that are known to cause interference.
You can also try going into your hub settings and manually changing the WiFi broadcast channels after scanning with the use of a third party app to look at what channel numbers are not congested in your area. I Personally use 'WiFi Analyser' but there's lots of others available.
