Thanks everyone for your input!
I think I mis-spoke earlier.

I haven't "checked" before about the hardness of his shell, I just recently noticed that it was soft and flexable. It may have been soft all along?? It's good to know that hatchlings tend to have soft shells.
I haven't checked the ammonia levels. I was just warned by a pet store owner that ammonia can build up and harm turtles. I've started using a water conditioner to get rid of the chlorine because the tap water in my town uses a lot of chlorine to disinfect the drinking water.
TheComputerGremlin.... you asked "What is your setup like? Tank size? Gallons of water? Filtration? Basking area?" I just upgraded his tank to a 20 gal tank that's filled with about 15 gal of water with rocks/bricks and a stick for basking/ climbing. I have seen him bask over the weekend since I posted this thread. He now has a Tetra Whisper 30 Power Filter (that has mechanical and biological filtration).
SpotsMama....I do change the water regularly. Thanks for the heads up. I have been thinking about water plants. Any plants you suggest to keep the ammonia low? The pet store in town has only a few plants to choose from.
industrial_girl_2000...He has a UVA/heat light (Zoo Med basking bulb) and a UVB light (Exo-Terra Repti Glo 5.0 Compact Tropical 26 watts bulb). The water temp is usually around 76-80 degrees. I haven't measured the temp of the basking area, but the heat lamp is about 7 inches or so from the basking area.
What type of thermometer should I use to measure the basking area temp?
marisa... I have seen him bask before. He has resumed basking and after his tank was upgraded, I've noticed him basking even more. His basking area is relatively easily accessable. He tends to use a stick I have next to his basking rock to climb up there. Since the rock is also some kind of sandstone, he can climb directly on the rock from the water (I guess he can easily grab onto the sand particles in the rock). There are several access paths I've seen him use. He does not have "privacy" when he basks. Do you mean curtains or rocks around the area? I'm using a Exo-Terra Repti Glo 5.0 Compact Tropical 26 watts bulb.