Last night while smoking a Cohiba I found small cracks opening up about an inch from the fire. These cracks weren't there before I started, or at least I didn't see them.

Maybe these cigars were too dry? Any ideas?

Probably over humidified. Sometimes that happens when they start to burn if they are wet, they expand. At least thats been my experience with a few sticks that were a tad bit wet and started to split at the foot.