u/Vakuta

Photo 1: Now, Photo 2: Before

I bought these lithops 2 months ago from Lowes and one of them started turning greenish-yellow. I don't know if it's rot, sunburn, or what. They're sitting in a southeast-facing window and I haven't watered them at all yet. The one that is turning greenish-yellow is facing away from the window to the room.

All of them have slowly developed some cracks in their skin and aren't as plump as they once were. They're in some kind of dirt soil with a small amount of pearlite, and it feels bone dry. I wasn't sure if I should repot them into better soil so soon after getting them, and I've been afraid to water them in case it is water rot.