I've always used the cheapest vodka (nobody drinks that!) and stuck all parts in an ultrasonic cleaner I got from Harbor Freight Tools. Run it twice (3 minute cycles) and your stuff comes out sparkling clean. Some folks swear by distilled water instead of vodka, but I get great results...so I haven't tried it yet.
I don't use a Protank mini, so I'm not sure if the
tank is plastic or glass. But, if plastic, you might be using juices that are known to fog up plastic. something like cinnamon or fruit based with loads of acid.