Launch file getting launched partially

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I am using STDR simulator to carry out a simulation wherein five robots wander randomly in a single rectangular arena. So here every robot is a ROS node. I have created a launch file in which I am launching the STDR simulator and five robot nodes. The simulator is launched properly but instead of five robots only two run. Basically how should I create a launch file for launching multiple robots in STDR robot? What should be changed? Help is appreciated! TIA