yea im sure in excess it would be I have never used it and have never worried alot about them slowing down a little. I just make sure they have fresh water and food at all times and that seems good enough for me. She isn't acting funny in any way is she?
Right does sound a little wierd do you have other hens that are laying......and are they just not able to free range at all? You may also try giving them a little caffiene or ceyenne pepper i've heard this helps with egg production.
may just not be quite into the swing of things yet......I dont know a whole lot about the breed so im not sure how good of an egg layer they are but may just take her a bit to get into a routine. How much daylight are you getting right now?