Why does my one cat eat out of the other cats bowl? Never used to happen!?

I have 2 cats. For years, they have been eating out of separate bowls, but in the past few weeks, the more dominant cat has been eating out of the other cats bowl. I dont mind, but I am worried that the less dominant cat might not be eating as much due to this. Any suggestions on how to get this to stop or reasoning as to why this has been happening. I have personally had some life changes, and am not home as much. Could this be a retaliation effect?