Advice needed/wanted.. Knox has been sick and teething his top 2 front teeth and just doesn't have…

Advice needed/wanted.. Knox has been sick and teething his top 2 front teeth and just doesn't have an appetite.. bottles1-2 ounces every 3-4 hours, baby food, real food maybe 5-10 bites.. he sips on juice all day.. was thinking about trying ensure until his appetite is back.. is this just a phase? What do your other mommys think? TIA