My dog had the same problem, and he also liked to obsessively lick and bite his feet for what seemed like hours. Turned out to be a yeast infection indeed, which was probably making his feet itchy, hence the biting and licking. An imbalanced diet is what causes yeast infections, including not having enough beneficial bacteria in the gut. I fed him Pedigree Adult dog food for the longest time, only to discover recently that there are some pretty unhealthy ingredients in there! I think switching to a higher quality, grain-free dog food is a great idea, especially one that contains probiotics.
Best of luck!
