Minimizing 120VAC relay EMI

Hello all. I have attached a portion of my circuit for a pcb that regrettably has to be mounted above a low voltage board with the MCU. The relays are driving 120VAC relays that draw around 1Arms. The 5V isolator should protect the digital signals, but due to proximity I'm assuming, when a relay disconnects power the ringing sometimes causes havoc with the digital circuits that are underneath this board. I have replaced the AC TVS diodes with 180V ones (ya I screwed up and forgot about the whole sqrt(2) rms of 120VAC and blew up the first diode). But I would also like a relatively inexpensive low pass to further protect my digitals from these spikes. Any suggestions? Thank you

 

Here's a screen grab of the ~300v ringing when a valve closes and the relay disconnects for reference

 

Thank you. I didn't realize I could use the flybacks on an AC relay. I'll give that and the caps a shot.

 

I see what you mean. Thank you for clarifying. I even put notes on the schematic to add flybacks. I will do so.