I've had this coco worm for 8-7 months and its always been happy and healthy. It's only been in two different spots during those 7-8 months and was happy. It's growing a new tube and was out almost all the time. All my parameters have stayed the same. Ammonia, zero, nitrite, zero, nitrate between 5-10. Last couple weeks he's been staying in his tube more and last night he shed half his crown and today he shed the other half. Is this normal periodic regrowth? This is the first time its happened.