@Geoff103 

Thanks for your requesting. 

It is rare that all the 5 smart plugs are unreliable, so I assume that it is the common wireless connection, which we can do some troubleshooting on it. 

First, try to power cycle the HS100 and the main router to verify whether they can reconnect to the host wifi. 

If still the same, you can pick up one of them and hold the settings button for 10s and reconfigure it; after that, you can check the firmware version and the signal strength on the device settings page. And take some time to test its performance; you can add the rest smart plugs one by one then.

May it help and have a nice day.