Maybe the turtles are not happy or it getting boring of the same foods it had been eaten. Here are some foods that you can feeds them.
Protein: Boiled eggs, meal worms, snails, crickets, earthworms.Vegetables: Corn, beans, beets, carrots, peas, squash, yams.Greens: Carrot tops, lettuce, collard greens, kale, spinach.
Hope this help