Welcome!What Hardware version is your router? Look at sticker under router.
What
Firmware version is currently loaded? Found on routers web page under status.
What region are you located?
I would disconnect every thing from the router, wired and wireless accept for ONE wired PC that you know isn't infected with anything and do a factory reset of the router. Disconnect the ISP modem from the router a well, just the PC and the router. See if you notice any log entries after the factory reset. While this is going on, run scans of all PCs to make sure nothing is infected. Run MalWare Bytes, a good program to have.
After the reset and if nothing is reported in the logs, connect one wireless device to make sure it connects just to the router. Review logs again. Make sure you set up wireless security for WPA2 and AES only is prefrerred, or Auto. Also set up the routers log in password with something new too.,
If all is still good, connect the ISP modem and review the logs and check internet connections.