An internal crack won't necessarily leave any evidence (outside leakage). The water is going down the drain. With it receding only an inch, I tend to wonder if the bowl is overfilling. Not having any experience with the Cimarron and your toilet in particular, I can't answer for sure. If it came from Lowe's or The Home Depot, you should exchange it now before any more time goes by.
Several years ago, I got a GREAT deal on a dark green American Standard pedestal sink and elongated Cadet that someone had ordered from The Home Depot and never picked up. (This was in '96, before the second generation of 1.6 toilets and the first 1.6 Cadet was TERRIBLE.) Once installed, all of the water drained from the bowl between uses. I pulled it, took it back and The Home Depot ordered another for me at no charge and with no argument.