Diagnosis
This is hard water detergent residue. It occurs when detergent does not fully dissolve and rinse away, often due to low water temperature or insufficient water flow.
How to Fix It
Use a detergent formulated for hard water. Reduce the amount of detergent if you have soft water. Ensure the water heater is set to 120°F. Clean the filter and spray arms to ensure full water flow. Run a cycle with a dishwasher cleaner or two cups of white vinegar placed upright on the top rack to dissolve existing scale.
If That Didn't Work
The water softener setting in the dishwasher's hidden service menu may be incorrectly configured. For hard water (over 8 grains per gallon), the setting should be increased to extend the fill time for better detergent dissolution.
Heads Up
Powder or tablet detergents can contribute to this more than gels if the pre-wash water is too cold to dissolve them. Always use a rinse aid to improve sheeting action.