A surprising number of people end up with thirsty chickens, for a variety of reasons:
--they don't provide enough water (especially in hot weather)
--they don't check or refill the water often enough
--the water leaks or gets knocked over
--the water freezes while the person is away at work or school
--the person gives fresh water in the morning, but it re-freezes without them realizing it
and probably quite a few other reasons as well
You hadn't said anything about water, so I mentioned it because it does affect how much food the chickens will eat. And because other people read the threads too, it serves as a reminder to anyone else who might have forgotten how important water is.
Many things are obvious to some people but not to others. I didn't know which ones are obvious to you. Most people who talk about trying to make layers "gain weight" are misguided (because they think a layer should be round like a meat chicken, or because they think she should weigh the "right" number of pounds for her breed even if she is actually a smaller bird, or because they think a layer should be extra-fat for the winter.)
You might be right about your birds needing to gain weight, but what I saw in this thread wasn't detailed enough for me to be sure of that. And if your birds always have free-choice feed and water, and they are still too skinny, that is definitely not normal. So I would suggest checking for problems (maybe internal parasites? Or some birds bullying others so they cannot eat or drink freely?)
