Wow, gnarly looking lake! I assume you are fishing those coves during the spawn? Its hard to tell without knowing depth and structure, but my guess is that the coves you are catching in are protected from wind and current. The coves that have creeks running through them may have current or rising/falling water, which is less than ideal for spawning Crappie. Also, they are more likely to keep moving on up the creeks to spawn, which is why they are not in the coves. Just my .02, I could be way off!!
C.J.