Since multiple devices from different manufacturers are having the same issue, I think it would be a good idea to test the mobile devices on a different network to see if they work. That way you can isolate the issue to being with the router/modem or not. I see you have already restarted the router/modem, and forgot the network settings on the devices, but allow me to offer this article for assistance.
iOS: Troubleshooting Wi-Fi networks and connections
This section in particular:
- If you are using a public or commercial network that requires a login or subscription, see this article for more information.
- Check to see if you have a self-assigned IP address:
- Tap Settings > Wi-Fi and locate the Wi-Fi network to which you are connected. Then tap >.
- If your IP address is 169.254.xxx.xxx, see this article.
- If you do not have a self-assigned IP address, see if other Wi-Fi devices on your network have Internet access.
- If they do not, consult with your network administrator or ISP for further assistance.
- If they do, reset network settings on your device by tapping Settings > General > Reset > Reset Network Settings.
- Note: This will reset all network settings including: previously connected Wi-Fi networks and passwords, recently used Bluetooth accessories, VPN and APN settings.