Finn will sometimes do that too---not want to eat his morning meal but will eat his pm meal. Does Ollie seem very hungry by the time his evening meal rolls around? does he get snacks thru the day? And does he look like he's lost any wt or has less energy? If he continues to eat only his evening meal maybe you can increase the amount he eats gradually so he's not losing wt/nutrition. I know some folks who feed their dogs (not bullies) once daily so it's not that unusual.