-Personally- I supplement with fish oil, vitamin E, B-Complex, vitamin C and glucosamine/chondroitin (Joint supplements) at minimum. I also give my dogs a multivitamin and garlic. I take these vitamins for myself too despite having a healthy, low processed diet. Just because you eat well doesn't mean there is no reason to supplement. At the very very very least, you should give fish oil and vitamin E. (And take them yourself each day as well) Fish oil has amazing benefits for yourself and your dog and the vitamin E helps process it properly through the body. Kibble diets are ridiculously high in omega 6 oils and ridiculously low in omega 3 oils, this is where many health problems stem from and an issue even in us humans when we eat an over processed diet. (Which kibble is) Fish oil supplements will help balance out the O6:O3 ratio for better health.
I also recommend supplementing with fresh foods such as meat (preferably raw) and raw bones (Never feed cooked bones - they can splinter), eggs (raw, scrambled or hard boiled), cottage cheese, plain yogurt, even veggies now and again if your dog likes them. Fruits are rare in our home due to being naturally high in sugar. No kibble is "complete and balanced". It's just not. So long as the majority of animals tested on the food live, they can slap a "complete and balanced" label on it. There is a BIG difference in an animal or person who survives, and one who THRIVES.