I have 10 BP's in 2 identical racks, with identical setups and have 1 Bumblebee that will sit in the water bowl for a day at a time. I wouldn't go crazy worrying about why. Mine eats once a week like clockwork. As long as yours is eating and is shedding properly, and isn't more moody than normal I wouldn't worry too much about it. Yours might just like the water.