If physically unplugging the power cable from your Rachio has not helped, it sounds like a problem is with a zone valve itself.
Possibly debris are preventing the valve from closing, or calcium (among other solids) has built up over the years. This is why it is often a good idea to have a backup, a master valve (though if master valve failed earlier, it may not be as apparent, so take any usefulness of such a backup with a grain of salt).
Overall I would recommend you check youtube on how to clean your particular valve model.
Hopefully you can fix it without needing a replacement.
Also please make sure that solenoid is fully screwed in, on the valve. It may have came loose, or a rubber gasket has worn out. If it is leaking air, the valve will not close.