when they are little hatchlings like that, they need more protein in their diet than older turtles. BUT it is a fine ballance. too much protein can casue shell deformities. so make sure you at least OFFER them some leafy greens like kale, spinach, even dandilion leaves. my turtle LOVES anacharis (aka elodea). also dont over feed them. turtles, especially babies like to BEG for food. swimming in front of the tank when they see you. resist the temptation and only give them 2 meals a day, as much as they will eat in 5 minutes. also, a reptile dust is a good idea to give them all the vitamins (esp. vit.d and calcium) that they need. i feed my turtle freeze dried food 2x a week somewhere out of the water (i do it on her basking rock) and dust it with the vitamins. she takes a munch and plops back into the water to eat. aquatic turtles need to be in water to eat.
have fun with your turtles. they are reallllly cute. too bad they grow up so fast...but they are still cute then too.