I've used branded hubs before which have a limit on the number of concurrent active IPs they'll support, and once you get up to the limit, it begins to drop the connections at the top of the limit. Restarting usually sorts that, as your main connections get back on at the start of the chain. May be that your hub is OK but it just has a limit on the number of concurrent connections.
The hub is only handling half a dozen WiFi devices. Unless someone has cracked the password and is bombarding it with extra devices there is no way I'd fill the IP allocation within a day.
I've used branded hubs before which have a limit on the number of concurrent active IPs they'll support, and once you get up to the limit, it begins to drop the connections at the top of the limit. Restarting usually sorts that, as your main connections get back on at the start of the chain. May be that your hub is OK but it just has a limit on the number of concurrent connections.