Has anybody else got a young gsd with grey ears?

this is a female dog who is a rich blk and gold colour and 20 months old but she has grey hairs on her ears like noticable but they come and go,is this something to be worried about. she doesn't have red ears (inside) or itch at all, she has regular worm flea,vaccs etc etc also garlic capsules too, is this just her coat changing as it does go back to gold/red it happens noe and again,she does however play withour other gsd who like knits her not chew ad they are always playing a lil rough but shepherds do,they are split if they get carried away. if any thing i think it could be an allergy as she had problems with a very well known dog food brand that is often reccomended here in uk but i took her off that cos that caused other probs too,she has had her skin tested for parasites etc on a routine check also for piece of mind and all were clear.her coat is fine other than that,and so is she,her bro has very tiny grey on his ear very small he is 3 yrs is it her colour like i think as in her background there is also sable colour dogs and her mum has the grey flecks through her coat called ***** i believe, sorry for long q just wondered if any one else had similar b4.any reccomended food as may be her food still..thankyou very much :)