I have a 6 mth 2wk old German Shepherd. His left ear is sometimes up other times floppy. Should I be worried?

His left ear from about 2months old was up and down, but mostly down. His right ear has always been up. At 5 months his left ear went up and stayed up untill a few days ago. Then it flopped down and has been down for 4 days now? I hope it will go up again. He is now 6 months and 2weeks. Should I be worried. He has a good diet of Royal Canin German shepherd junior food. Please let me know what you think.