Bok Choy is actually a feed ocassionally item it is also high in vitamin A which is not good for beardies. But ocassionally like maybe a few times a week just not meant to be the daily staple item in their salads.
I often buy one or two heads of baby bok choy and add it into their salad for the week. Because the heads are so small, they only get a few pieces per day and its not enough to overload them.