this morning when i checked on my millipedes my larger one was just sitting in the corner. i picked him up and he was kinda limp. a few of his legs were moving but not very much. they have plenty of food and water. i have plants in the cage also but i've had the plants in there for a while now and the millipedes were okay ,so i know its not the plants. could he be molting. please help. thank you in advance.