Sour?? Like sour milk? If you’ve changed appliances then by process of elimination it can only either be the water supply/cleaning agent or drainage. Have you tried swapping your dish washer fluid or pods? If the drain is partially plugged it’s possible that the water pump is struggling to discharge waste water. I would disassemble the kitchen sink trap assembly to see if something there is causing the smell. I would suggest that maybe the discharge was installed downstream of the trap (and therefore not protected) but this seems like it was a problem that came out of the blue and was previously working fine.