Chicken weight question...
I’m not familiar with the internal workings of every hatchery here in the US, but I’m pretty sure some use what the chickens should weigh in their advertising while others actually weigh their own chickens. You’ll see different hatcheries give different weights for the same breed.
There is another factor too, that’s the way you feed them. The way you are feeding them sounds great to me by the way, but chicks that will be show chickens are generally fed a special diet so they grow bigger and have nicer feathers than our chickens. A big part of that is genetics but part is diet too. Diet is one of the many reasons show chickens cost more than hatchery chickens. They just cost more to produce, let alone a lot more work. Some people that raise show quality chickens do let them forage for some of their food, but once the special ones are identified they normally get treated special. Everybody does things differently.
Letting your chickens free range lets them control to a large extent the diet they will eat. Part of this depends on the quality of forage you have, but birds that forage a lot tend to not eat a really high protein content diet. When you let them forage you lose your ability to micromanage their diet.
It sounds like you are raising yours like backyard chickens and that they have a great life. Unless you really want the larger chickens, I don’t see that you have anything to worry about.
Weight can affect laying ability if they are overweight. Fat deposits are usually in the hind region, and too much can make passing eggs difficult. If they have access to a balanced feed, plenty of room to range, and aren't fed too much scratch, they likely won't get too fat.
As far as egg size goes, pullet eggs start out small and will gradually increase in size. Eggs will also get bigger after each seasonal/fall molt.
Before a hen starts laying she adds some extra fat. A lot of this is in the pelvic region (known as a fat pad) but some is kind of scattered all over. If you butcher hens that are laying you will definitely see this. Even hens that are not laying generally have more fat than a rooster.
This fat is there for a reason. When a hen goes broody she does not need to get off the nest much to eat and drink. She mostly lives off this excess fat. Even if a hen never goes broody she will still build up some excess fat before she starts to lay just in case.
It is possible for a hen to get really obese. Obesity is not healthy. It is extremely unlikely yours are going to get obese with as much free ranging as they do. Not only do they get exercise they are going to balance their diet fairly well with that forage.
There can be another problem if hens are fed too rich a diet, especially protein rich. Too much protein can cause a hen to release extra yolks to start eggs. If the extra yolk is released at the same time as the other, you might get a double yolked egg. If it is a little later you might get two eggs in one day. The hen only makes a certain amount of certain materials for the eggs in a day, so the second egg could be weird, maybe small, maybe soft-shelled or even shell-less. If two eggs are in the shell gland at the same time they can get some really funny markings on them. Again with yours foraging you are extremely unlikely to have this problem on a regular basis. An occasional hick-up is not cause for concern. It can happen to any of them.
On the other hand if a hen does not eat a good enough diet she can’t build up enough fat to lay eggs. That condition is really rare but it is possible. You feed yours better than I feed mine and when mine are laying they normally lay a lot of eggs, several days straight before they take a day off, then they do it again. In my opinion, a hen that spends a fair amount of her time chasing creepy crawlies and scratching in things you don’t want to think about is a healthy productive hen, especially if she is offered the nice things you feed her.
One downside for some people is that the more protein they at the bigger the egg they lay. My hens don’t lay double extra huge eggs, they lay a lot of decent sized eggs that are a healthy size for them to lay and that produce a nice healthy chick when I hatch them. I’m OK with that. I’ll exaggerate to make the point. Think of a woman giving natural birth to a 10 pound baby versus a 7 pound baby. My wife gave natural birth to a 10-1/2 pound baby. She was fine afterwards and so was he but she would not recommend that to anyone.
As clearly as I can say it, I think you are doing fine.