Hey so I have a res that I'm not sure how old she is, I inherited her from a friend. But she is about 4.5 inches because she was kept in a container too small. I've had her for about 7 months now and a month and a half ago she started showing some bumps on her shell. They aren't soft or smelling or anything and she is just as active as ever. She is currently kept in a 40 gallon tank with a good basking area and clean water and fed pellets and collard greens.
A small tank would not restrict her size. The shell issues are usually from a combination of poor diet/irregular diet/lack of calcium/lack of vitamin D3. The shell isn't so bad that correcting her diet and habitat will help tremendously. After a couple of sheds, she will look much better.