Cricket are clean creatures and appreciate having a clean living enviroment. You should aim to clean your cricket container at least once a week or if you notice a build up of moisture, poo, mould etc. If your crickets are dying and you have made sure that temperature, humidity, ventilation and everything else is set up right it could be due to a problem that you can't see with your eyes such as germs or mites. To combat these potential issues, thoroughly clean your container at least once a week and spot clean as necessary.
To clean your container place your crickets in a temporary container, box or bucket. Take out any food and water containers and any cricket housing such as egg cartons from their regular container. Tip out any left over food, poo, shedded skins etc that may be on the floor of your container. Next spray the sides of your container with a cleaning agent such as vinegar (do not use harsh chemicals as you don't want to risk transferring it to your pet when you feed your crickets to them.) and wash the whole container with hot water. Be sure to dry your container properly before returning the housing, food and water containers and crickets back in. Make sure you replace any egg cartons that are starting to look damp, too dirty or smelling bad.
Don't forget to regularly check your crickets water source to make sure that their aren't any dead crickets, poo, or food in it. Wash the container and fill with clean water often.