Hello I noticed after about a week of use there looked to be a rust colour in the bottom of my hp-c plus cup. I stopped and cleaned today and it looks like my brush is getting rust in the bottom of the cup and it’s creeping up inside the cup.It’s only discoloured at the moment. Just asking if this is normal, I don’t leave it wet and use Iwata cleaning solution plus tap water to wash it through. I make sure it’s dry after every use so just asking if this is normal or something I may be doing wrong? I have bought some distilled water as I do live in a hard water area, my wife has an RO unit as she has a marine fish tank so could I use ro water instead of distilled?