He probably doesn't like those hides you have because they don't make him feel secure. They are WAY too tall, snakes like something that is right above them. Also, light comes through them because of all those holes, so they don't seem like hides at all to him. I would say replace them with something that will keep it dark, and lower to the gorund, or cut those in half and cover up the holes with something. Replacing them will be easier and more effective. Go to a dollar store and buy a shallow plastic bin that blocks the light well. Then cut a hole in one edge to maximize the dark area inside.
I think that should help.
Oh, and your humidity might be higher if your water dish is over the heater at all. Just slide it to the cold side if that is the case and see if that changes things.
Good choice with a ball.