Hi,
How long have you had it in total?
I ask because we normally see cruising as an indicator of stress. Out for a couple of hours at dusk night or dawn is one thing but constant cruising is nearly always a stressed BP.
I know the others in the rack are fine but could you run us through the setup anyway?
It's also possible he is simply more nervous than the others and might need some extra security before he feels comfortable enough to eat.
dr del