An idea
that was recommended by someone else on this forum. When you're ready to run your machine with dirty dishes, put your detergent in the main detergent cup......close it and pour like a shot glass of liquid bleach on the dishwasher door, close it up, start it. I'm not sure what kind of regular dish machine detergent you use, but it shouldn't be affected by the bleach since it will be mostly rinsed away in the first water purge. I've been doing this for a LONG time now and it I use Finish powerball detergent, which has enzymes.....the machine smells santized and dishes are really clean. No tomato stains......I don't pre-rinse. OR....... You could be a bottle of chlorine-based detergent, pour a little in the prewash so that will give enough bleach action in the prewash to get those stains off.....but I like the regular bleach better. I think it keeps the inside of the dishwasher cleaner as well.