Hidden Home WiFi Network on iPhone

What is causing my 2.4 GHz home wifi network to show as connected albeit with a Hidden Network attribute under the name when selected in Settings on my iPhone? No such annotation on my iPad mini or on my MacBook Pro!

Checking on the Router Wireless Setup pages in my browser, I could confirm that Hide SSID is off & Enable SSID Broadcast is definitely ticked on both the 2.4 GHz and 5 GHz networks. Admittedly I have two routers connected in bridge mode via ordinary Ethernet LAN connectors (neither WAN) on both routers so they should be effectively operating as a single network. The same network names are being used on both routers. DHCP is on for just the primary router connected to the NBN phone line but not for the secondary client router. Furthermore, there are about 33 wireless devices being juggled usually quite well although occasionally a couple of cameras lose their connection with the slower network.