When did this start to occur on your Mac models and iPhone?
It has happened twice over the last week
What exactly shows when you mentioned it 'forgets' the Wi-Fi network password?
I notice I am no longer connected to my home WiFi. I select my usual home network from the available WiFi networks and am then presented with the password dialog box to enter the password. Usually I would be automatically connected to my known home network and not have to enter any password.
Are other Wi-Fi network acting the same way, or just the one you're using currently?
Just my usual home network - which is the only one I use at home.
Sometimes unexpected behavior can be resolved with a restart. Check out Restart your iPhone and the section ‘Restart your Mac' here: Shut down or restart your Mac We also recommend restarting your Wi-Fi router(if this is your home Wi-Fi network).
I've done all these and after two days so far so good