This was a new Perception roll and does not take one of your actions. It should take place after you stride to D8 and before you take your two remaining actions.
[sblock="Perception 15+"]The ceiling above C7, C8, D7, and D8 looks unnatural.[/sblock][sblock="Perception 20+"]The ceiling above C7, C8, D7, and D8 looks unnatural. A rope leading from that area to a pulley and hangs down from the ceiling in D5.[/sblock]