TailsWithScales

Is it still a screen top?
Is it covered other then where the light sits or uncovered?

I personally use a mix of top soil, sand and peat moss. You can get all this stuff really cheap at Home Depot or Lowe's. I think even Wal Mart sells it all. Mix equal part with water until it clumps but does not drip. You could put about 3-6 inches that cage. The top is fully secure????

Ditch the hot rock. With proper lighting it's not needed anyway and even a low temp heat rock can burn a monitor's belly. The belly skin is much thinner then the skin on their back. Any discoloration compared to that normal white or off white is more then likely being caused by the heat rock.