How hard is your water?
Some detergents, I've found, just leave residues (spots) on my dishes. Our water is so hard, it's technically "off the scale". We've really had to experiment with different detergent brands to see what would work for us. None of the liquids or powders seemed to work, whether they were store brand or name brand (which was disappointing, since those are often cheaper). Tablet formulas seem to work the best for us, especially if they have a rinse agent like Jet-Dry built in.
I've only found one environmentally friendly one that seemed to work for us -- Ecover dishwasher tablets. I know Method makes a tablet version, but I haven't tried it.
There's another dishwasher additive that I read about not to long ago (on the Pioneer Woman website? I think?) that's supposed to be amazing for getting your dishes clean and shiny when you have hard water, but I haven't been able to try it yet. It's called Lemishine. It's a powdered citrus based formula that you add to the detergent cup along with the detergent. It is also supposed to help keep mineral deposits from ruining your dishwasher. The only reason why I haven't used it yet is because I haven't found it around here!