They can recover from this, and can jetisen their crown from time to time as a normal occurance a few times throughout the year.
However if it seems to happen every month then the chances are that it is starving, irritated or otherwise plane unhappy. In this case the crown will come back smaller and smaller until it dies.
You should be adding phytoplankton to the tank. DT's phytoplankton is a favorate live type. Kents phyto is also been used with success.
Try to feed it by injecting into the current a few inches away from the crown with the current heading to the feathers.
Thomas
