I have had a similar experience with my birds. I let them free range and the feed in the coop did not seem to go down very much. Turns out that they will and have the ability to regulate their intake, in as far as the needs for nutrition go. It is kind of unnerving at first, and I was quite concerned, but it turns out the birds are doing just fine. I suggest you leave the food free choice, and not remove it. Every now and then my chickens seem to have a slow bug day and will come in and pound the feeders.
I let my birds out into a place that had not had free range birds prior, so there were LOTs of 'things' for them to chose from. They would not even come for mealworms. I am sure they will in December, but not now. Anyway, that is my experience.
Best to you and your birds,
RJ