hi , i have two , 2yr hermans. i have noticed one of them ( frankie) goes up on all four legs and rocks backwards as if he is straining! then a triangular shaped bit appears and he drags it along until it goes back inside .! looked like his insides..... he seems ok ...eating ,drinking and playing with his brother/sister(bennie)...could anyone tell me what this is? and should i be worried? thanks