DIAGNOSIS That's corrosion from dishwasher detergent, specifically the strong alkaline agents in dishwasher pods or powder. The "dishwasher safe" claim is for the parts, not longevity of the finish; aluminum reacts badly.
FIX Stop putting the main pot in the dishwasher immediately. Wash it by hand with mild dish soap and a non-abrasive sponge. For existing spots, a paste of baking soda and water can help polish them out gently, but deep etching is permanent.
IF THAT DIDN'T WORK If the spotting is severe and you're worried about material integrity (unlikely for just spots, but if it's pitted), contact the manufacturer. They might have advice, but this is generally considered cosmetic damage from improper cleaning.
HEADS UP The stainless steel lid and other components are fine in the dishwasher. It's specifically the raw aluminum cooking pot that gets wrecked by machine washing. Hand-wash only for the pot.