esp8266 + octocoupler relay: WDT reset when using AC current
To prevent EMI and to save the relay contacts, you could switch the relays at AC zero-crossing. Add some kind of zero-crossing detection to you project and before switching a relay, wait for a zero-crossing and then wait just before the next zero crossing (about 9500 microseconds at 50 Hz AC). 

Simple is to use a current sensor to detect zero-crossing. Current AC wave should be aligned with the voltage wave, if there is no shift in power factor.