Erika,
I am not sure what it could be, but just in case you should maybe get a stool sample of your dogs. Also you could contact Diamond and see what info they have if they are keeping record of complaints and reports. I am stuck currently on what dog food to buy, since this brand has been recalled. I do not have many dogs as you do, but I do have 2 big dogs and another one coming soon. Cost is always a consideration, as well as safety and quality. Currently, I have switched to Flint River, but I cannot give you any personal feedback on this brand since I have not used it long enough.
All the best.
