if the dishwasher leaves solid detergent on the dishes, try using less detergent (just one teaspoon of powder) and/or switching from powder to liquid
if there is hard water, there are some products for that, e.g. https://www.google.com/search?q=cascade+hard+water&oq=cascade++hard+water
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some things you might want to have if guests are coming over:
all of those items should be relatively clean.
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