IOWA CITY — On the third night of marches in downtown Iowa City, the crowd size Wednesday night had more than tripled to nearly 1,000 people. One of the most frequent chants among the throng pulsing through the city streets for more than three hours was “no justice, no peace.” But while the group was boisterous, occasionally blocked traffic and spray painted streets and buildings, there were no apparent clashes with law enforcement early in the evening.