There are three important instructions for the journals:
First, just pick one thing to talk about – a claim, argument, position, etc. I prefer a deeper treatment of a smaller scope over a superficial treatment of a broad area.
Second, the first half of your journal should be spent explaining the idea you want to discuss. Be sure to not spend more than half the journal doing this.
Lastly, the second half of the journal should see you responding to and evaluating the idea you presented. Tell us what you think of this idea – it is useful? Misguided? Needs fixing? Be sure to not just register your opinion, but to argue for it. Defend your stance as much as possible.