How much to feed 6 golden comets?

Ok, so I know this might be a crazy question and I know there are probably a ton of answers, especially after browsing previous posts, but we have 6 golden comet pullets that are 12 weeks old, We are wondering how much feed is too much ? They are growing quite large already. We bought them to be layers so we would prefer that they not get overweight since I have heard that this can cause complications with laying. I am also concerned about rodents taking up residence around the coop yard because of the easy access to the food. "The Girls" are still on their starter grower and they get fed twice a day, but the food is not always gone when we go to feed them, so my main question is, Does anyone have an exact amount of food that would be right for my little flock? Any responses are appreciated.

Thank You!

Thank You so much for your response, I am a newbie, obviously, LOL, but I want to make sure that I am feeding them properly so they get the nutrition they need since they are still growing "girls".

Thanks for the responses, my pullets are in a enclosed yard, it is relatively large, they stay in there during the day and in the afternoon we allow them to run around the yard (with the dog,LOL,she thinks they are her flock) while we are home, on the weekends they get turned out about 8am and we let them free range for the day, once again, while we are home. Generally they get about 2-3 hours out of the pen on weekdays and sometimes up to 8 hours on the weekends, average is about 5 hours. I give them grapes to play with and eat, cut in half, they really love them, not too crazy about greens I give them, but they will pull up and eat grass all day long.