The house I live in was finished 6 months ago. Ever since I moved in, I have seen these three dark spots on the wall up near the ceiling in my laundry room. Both that wall, and the wall adjacent to it, have the garage on the opposite side of it. The laundry room isn't humid/damp. Ever since I moved in I have had a dehumidifier in there, as well as a gauge that shows the humidity never gets above the 40's, even with both the washer and dryer going at the same time. I've tried cleaning or wiping down those dark dots, but that doesn't do anything. I've also noticed that there are some more, much lighter colored ones along the wall going downward. I don't burn anything in the house, candles, incense, etc, due to allergies/asthma. The spots don't seem to be bumped up on the wall when I touch them like I would have thought screw pops would be. In addition, the other day, while trying to figure things out, I pulled out my dryer and I realized that there is, what appears to be rust, on the metal box around the dryer vent hose. It even seems to have dripped down onto the bottom part of the box. The dryer hose was/is hooked up properly, no leaks or holes in it. If anyone has any ideas why these things are happening when their isn't excess moisture in the air in the house, I would greatly appreciate it. I'm not sure what to do at this point. Thanks!