It sounds like all of your RHP's are on the same side if I am reading correctly. I would alternate sides, and stagger them cage to cage. That way, the residual heat loss from each tank below, helps heat the cool side of the one above it. It could help stabilize your temps a bit more, and even make it to where you can keep your tstats set on the same temp for your hot spot without having to change it based on a minor swing in room temp. Just some food for thought.