Feed has protein with balanced amino acids, especially methionine, carbohydrates, fat, many vitamins, especially vitamin A and many minerals, especially extra calcium in layer formulas. It provides most of what a chicken needs. One thing it doesn't have are all the phytonutrients that are contained in fruits and vegetables. The natural compounds in plants that we have just begun to understand fight cancer, viruses, etc. I personally feel that chickens are healthier if they eat a wider range of foods that contain these phytonutrients. Eggs from free range chickens with access to pasture have also been tested to contain more of the good omega fatty acids and more vitamins. They're better for you. At the same time, an unbalanced diet can be very bad for a chicken.
The sesame and sunflower seeds you're feeding are helping to balance what you're feeding by giving them more and better protein. So are the eggs. If you're giving the type of sunflower seed that people eat, rather than an oil type sunflower seed, they have much higher levels of protein. I think the hulled of that type are 22-23 percent protein. Sesame seeds are really high in protein, I just can't remember how high. 30 something maybe? I need more coffee! They're two of the best plant sources of methionine.
A meat or fish based feed should have adequate methionine in it, but a plant based feed will need methionine added to have the correct amino acid balance. This will be synthetic methionine. They only other way is to use really expensive plant foods. Otherwise, the chickens either need to eat more of the feed or the feed has to have a higher protein level to satisfy their nutritional needs. Either way, some of the excess protein is wasted and the feed is not as cost effective. It adds more waste to the coop and run, too. Plus, if they need to overeat feed to get enough of an amino acid that's too low, they're eating too much carbohydrate and fat to get it. They can end up too fat. Or they may just not overeat as much, not get enough protein and not lay as well.
Most people overestimate how much protein is available to their chickens. They can pick a yard clean in a fairly short time. It takes a lot of protein to build and maintain a chicken. On top of that, they need enough extra protein and other nutrients every day to form an egg. If they don't get all that, they have to eat enough days to finally get enough excess nutrients to finally form an egg.
If you can walk through your grass and have lots of bugs, preferably including some good sized ones, popping up, that's plenty of protein. If you have a lot of leaf litter and you can go out and scratch through it and find a handfuls of worms and bugs every day, that's a lot of protein. Most people don't have that. Most people don't have that in the winter. Free range works better in a lot of the south, because they have a LOT of bugs there. An annoying amount, bigger than many other areas and for more of the year. It also helps if you have livestock, because then you usually have a pasture with legumes, spilled grain, and manure to scratch through. Free range also works better on larger acreage, with a more diverse and plentiful forage base. What I mean is if you are trying to feed your chickens mainly by free ranging them. If you are supplying a balanced feed, you can free range anywhere.
Chickens eat and get nutrients from grass. The also enjoy a wide variety of dark leafy greens. Favorites are chard, kale, collards, beet, spinach, turnip, dark leaf lettuce and any others that you would grow for yourself. They get the same health benefits from greens that people do. They will also eat the leaves of legumes like clover and alfalfa, that can provide more protein. A lot of different vegetables and fruits are good for them, for the same reasons that they are for people. Dark green, orange and red foods ensure that the chickens are getting vitamin A. Without it, chickens are more susceptible to upper respiratory infections. When it comes to diseases in poultry, that's a big deal. It's also traditionally one of the biggest killers of pet birds on a seed only diet.
Chickens have a lot of the same nutritional needs that people do. They do need more protein when molting, to grow feathers. During the time they're growing and maturing, they're constantly growing new feathers, as well as their body growing, so they need good quality protein. I think mine feather out better with more sunflower seed added to their diet. Any type of complete protein work well, too. They will often catch and eat mice, lizards, small birds or anything else that doesn't eat them first. They have no problem eating meat and if you kill it for them, they would probably eat any sized mammal down to the bone. The eggs you feed them are great protein.
It sounds like you're giving them a lot of good foods. I would just make sure that you don't give too many carbs all at once, especially the high calorie starchy type, give enough protein and don't forget to give them free choice calcium. Most people give oyster shell. Do you know what a good balanced meal looks like for a person? That's kind of what a good balanced meal looks like for a chicken. Not all pasta, corn and rice at a meal. It would have some beans or meat/fish/eggs and some dark green or orange vegetables with it. The sesame and sunflower are a nice addition, especially if you are feeding legumes in place of meat/fish/egg. If you keep what you add to the diet more limited in volume, you don't need to worry as much how balanced or nutritious it is. If what you are giving is a major portion of what they are eating, then it should be a balanced diet.
