I was cleaning my bike yesterday, as I had been riding in the wet and had kicked up loads of sand. As I was cleaning, I noticed a number of the teeth of the largest chainring were broken/worn down. There were a significant number of teeth that were rounded off. This is pretty surprising to me, as my bike is roughly 2 months old. Though, I have put roughly 350 miles on it already. I have an appointment scheduled with the LBS I bought it from, as they give a free check-up and tune-up for all new bikes.

Is there something I'm doing wrong? What could be causing it? How can I prevent it?