Which food are you feeding exactly,as in brand?Not all brands are good and some that claim to be healthy are very low quality if not dangerous
Some good foods in the US would be:Higgins Sunburst Hamster/Gerbil food(this must be mixed with another safe and high quality food with higher protein to be suitable),Mazuri Rat and Mouse lab blocks(not suitable on their own,must be mixed with an actual mix),Hazel Hamster(aka Harry Hamster in the UK),and as a last resort if you can't get Mazuri in store and don't want to order online but can get a secondary mix to add that is suitable Carefresh Hamster/Gerbil food which like Mazuri does not have enough variety on its own to be suitable.