Have you topped up your salt and rinse aid? In hard water areas you may need to add salt to help your detergent tablet cope with lime scale and impurities found in hard water. Check the container in the bottom of the machine has been topped up and that the water hardness setting is correct. In hard water areas the setting may need to be increased.
If you are not using 'all in one' tablets you may need to add rinse aid which is designed to prevent streaky marks building up on the dishes and glasses. Add the rinse aid to the compartment found in your dispenser and adjust the dosage selector until you get good cleaning results. Turn towards 6 or 7 to increase the dose.
Do not add rinse aid if you are using 'all in one' tablets