My turtle is about a year and a half now. He has always eaten good and I was careful to feed him a good balance of food. The problem is that he seems to have lost interest in his turtle pellets. He will swim around them, maybe even put them in his mouth and then spit them out. Is this a normal finicky thing or should I be worried? He will still eat everything else in his diet (veggies and dried shrimp as a treat)