I have a lg dishwasher, about 4 years old. Within the last few loads the stainless steel has started to discolor and turn into a rainbow color in one particular area, on the left side near the water inlet cover. It is only discolored around the bottom half and a streak down to the bottom of the dishwasher.. I have always used the same jet dry and soap that the machine came with since new. Can anyone tell me what the discoloration maybe coming from? Is it possibly heat related?