My dog isn't eating her food?

I have two dogs, Charlotte and Fitzgerald, who stay in a bedroom while my wife and I are at work. Every morning, we feed them the same type of food in separate bowls. For the past few days, I've come home from work to find that one of my dogs, Charlotte, did not eat any of her food (the dogs don't try to eat out of each other's bowls). I feed the other dog again before we go to bed. When I wake up, both food bowls are empty. I really hope Charlotte is the one who ate it. But why is she waiting until night time to eat, meaning she's only eating once a day?