You say only 2 hens are laying, does that mean yours are younger and not there yet, or older or just not laying for other reasons. If they are younger and haven't reached laying age yet, their appetites are enormous relative to their size. We have 12 hens and a rooster. A few old bitties, the rest were started 2 years ago. Before they started laying regularly, they would empty our 2 gallon feeder bi-weekly. Now it will last most of a week.
I've also noticed pelletized feed will last longer than textured. We once got some textured feed that had some sunflower seed mixed in. They would shovel all the rest out into the bedding to get at the sunflower. Perhaps yours have some special morsels in the feed also. Observe their feeding behavior.
As for rodents, etc, look for sign in close proximity to your birds. They don't like to travel far, if they are using your feed source, there will be sign nearby. Holes or burrows, gnawed areas at small openings, nests under wood or other clutter. Leave a paper towel smeared with peanut butter overnight near the coop. If it's shredded within 1 or 2 days you have a significant rodent problem. Other potential feed theifs include opossum, chipmunk, squirrel and raccoon. The O and R will also take eggs and occasionally birds.
