If he can see through the "wall" then he'll keep trying to climb over it. Put up a solid barrier (card board will do) so he can't see through. Provide shade and water too.
Do the strained carrot food for babies soak, as mentioned above. And I'd say for sure your temperatures are not warm enough, especially now since they are not feeling well. Try to raise the temperature to 90 to 95 degrees F and no lower than 80 F at night.
Just to add to the great post about deep shade you'll find that when torts want shade they will always favor shade under a plant or bush, rarely under a board or something similar. My feeling is they want that little micro climate that just feels better to them when they hide under and push up...
I have just 1 star but he has been keep in a humid closed chamber for the last 3 years and the shell is fairly smooth and he feels like a heavy paper weight when you pick him up. Never had shell rot and never had a respiratory infection. Which leads me to believe that indeed stars enjoy and...