A variety of food is better than sticking to just pellet food. Just make sure to NOT feed them iceberg lettuce. It doesn’t have much nutrients in it and turtles seem to really like it and not eat anything else.
Don't overfeed them though, since they beg for food.
Another thing to note is that if your turtle(s) is/are shedding on their shell, everything is fine and it's just that the turtle's shell is growing.