I hope you can help me - when I open the door to the ice maker there is a mildew smell - the ice is making perfectly - but when I looked all the way in the back of the machine I noticed this brown crud - my question is what should I do if anything? The crud is located on a long white pipe - I have never cleaned the back inside of the ice maker - if I have to clean it - what should I use? Please help me understand what is going on because I am older and don't know the language well. Thank you & have a nice day.