My red eared slider lost claws

by Angel
(Canada)

I just noticed recently that my red eared slider, which is about 8 months old, has lost a claw on both his back paws. One of his paws (on the righ) has like an orange-ish color where the claw was and what looks to be a bump and the other one (on the left) seems to be red like blood there the claw used to be. I have rocks at the bottom of the tank and i know they (i have two but the other is fine) like to dig alot in them. I was wondering if this is normal. Do red eared sliders loose their back claws sometimes?