Its purely anecdotal but I got a couple of tank raised clowns and qt'd them. They seemed fine, ate fine no problems, after a month in qt I dropped them in my display. The whole time they were in qt they stayed in one corner never ventured out, same thing in the display. These were my first fish I thought maybe it was normal. After a few weeks in the display I started noticing the stringy poop. I pulled them out back to the qt and treated with prazi, after the second dose they started swimming around the tank. After a fallow period I put them back in the display and they roam over the tank.
I don't know how common the behavior is, but if the fish isn't venturing out I would assume something is probably wrong.