joint_state_publisher reading only one joint from robot/joint_state

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I'm attempting to write my robot state to joint_state_publisher to be viewed in RVIZ, but joint_state_publisher is only reading one joint from each message. How do I get joint_state_publisher to update the entire state?

My node my_robot_simulator is publishing jointState messages at 10hz to topic /my_robot/joint_states, which is read by joint_state_publisher (also running at 10Hz). Each message contains seven joint state values.

example:

header: 
  seq: 210
  stamp: 
    secs: 1571243618
    nsecs: 169618145
  frame_id: ''
name: [j1, j2, j3, j4, j5, j6, j7]
position: [0.25346757744592685, 0.25346757744592685, 0.25346757744592685, 0.25346757744592685, 0.25346757744592685, 0.25346757744592685, 0.03767337887229634]
velocity: []
effort: []

But joint_state_publisher only updates j4. The other six joints never get updated. If each jointState message contains only one joint, then joint_state_publisher updates that joint as expected. But if I publish joint states one at a time at 70Hz, joint_state_publisher only manages to read a few of them, maybe 20%.

Is there some incorrect syntax in my messages? Is it a timing issue? It seems like we should be able to do just about anything at 10Hz. How do I get joint_state_publisher to update the entire robot, and not just one joint?