Yes, Red-eared sliders are one of the most common species to have their shells peel. Females, in particular, will get fairly large, and then begin shedding their scutes. If well taken care of, the scutes should peel off, but may come off as flakey pieces that peel when they bask. Over time, their shells will grow and they shed scutes in the process. This is totally normal, like kids losing their baby teeth, except if they were to do so regularly every few months into adulthood!