Bad smell on dishes

I have two dishwashers. After 17 years, I started getting a fishy bad smell on some of my dishes. I replaced both dishwashers. Smell in both continued. Replaced all hoses and garbage disposal. Smell continued. Had drain line power washed all the way from kitchen to street. Still smells. Replaced air gap (using a single air gap designed for two dishwashers). Never run dishwashers at same time and run garbage disposal before running dishwasher. Any suggestions?