smelly lips!

Gus has terrible breath sometimes even if I go just one day without brushing his teeth.He had to have his teeth cleaned when he was about 2 years old.He is (and always has been) on a good diet as is pippin and pippins teeth are fine.The vet had told me that gus may have a genitic problem with his teeth..something to do with saliva...he may be right as I brush their teeth every day and always wash in and under the gum flaps but while pippin is fine Gus looks like he'll be needing his teeth cleaned again soon.
I did try logic but found it just ok not great..I find brushing the teeth and gums with doggy toothpaste better. I was using my fingers for a good while as they wouldn't tolerate the brush,but I got a soft rubber finger brush a few weeks ago.