Xiaomi Smart Plugs going offiline

I’m wonder if anyone has experienced similar as i’m not sure where to start with this. I have recently added 3 of the Xiaomi Wifi Smart Plugs

I have one inside about 3-4m’s from my wifi, and another 2 outside in a weatherproof box to control a water feature and garden lights, the 2 outdoor are maybe 10m’s from my wifi.

All 3 plugs have a DHCP reservation set
Wifi is Ubiquiti AC-Lite and using Channel 1 which is the clearest channel for me.

The issue is the sometimes all 3 plugs will go offline at the same time and also be unavailable in the Mi Home app. When this occurs i am still able to ping all 3 using their reserved IP Addresses.

The router is a Fortinet 30E and i don’t see any events that would indicate anything is getting blocked.

Usually when this occurs rebooting them brings them back online