Finding a stain and odor on clothing after washing

My non-baaligh brother often has accidents. This time, when he pooped in bed, I threw the bedsheets in the washing machine along with his underwear which was first washed by hand, and set the rinse 2 times for a total of 4 hours. During the second rinse I even threw in some of my clothes. As I was taking everything out of the dryer, the stains from the sheets were completely gone, and all the clothes smelled good, but then his underwear had a very light brownish colour and some odor. Does that mean the underwear is impure and everything else that was washed with the underwear is also impure? I put everything in the dryer before I noticed any of this so does that mean the dryer has to be purified now? What must I do?