It makes perfect sense - Roc retired from training a few months ago. His activity level decreased and it never even occurred to me that his food should, too! And Dax has been having issues with her food for quite a while - she needed more protein. Which has calories. Which I didn't account for in the quantity I fed.
So we've started a new routine. Before my treadmill workout, the dogs get theirs. Roc took to it right away - he gets to watch tv while he works out. Dax had to be convinced it was fun, but she's getting the idea. We'll all be in shape before you know it!