shell damage

Hello, Noticed some damage to the underside of my 40lb Sulcata the other day. Can I treat it? If I can, with what? Thanks.

recently rescued a red eared slider and while wet the shell looks ok but when out of water and dried it gets very white around the edges of the scutes. I own another ReS and ive never seen this before? what could it be and how can I fix it? edit: I feel like i should also add that the turtle...