Bloodworms are much too high in protein to be an everyday snack. Let alone 2 cubes a day for such small turtles.
Quit feeding the Bloodworms and only feed pellets for a while. They'll take to the pellets when they get hungry and realize the bloodworms aren't happening anymore. Get a Reputable brand of pellets like Reptomin.
Read through this whole section:
http://redearslider.com/index_nutrition.html
There's tons of info in there for your turtles diet.
With foods like lettuce leaves, I just toss them into the tank mostly, Sometimes I take the time to put it in a suction cup veggie clip. (Veggie Clips are readily available at Petsmart for a few bucks.
I would try some red or green leaf lettuce or an Aquatic plant like Anacharis to start with. Keep in mind that your little ones are still very young and they might not take a liking to veggies right away. Most little ones don't like them for a while, or until they reach maturity even. But keep offering them anyway.
Also, You didn't mention Cuttlebone. It is sold in the bird section. You wanna get one of these, peel the hard backing off( the side you cant dig a fingernail into), then break off a chunk and toss it in the tank. This will give your turtles beneficial calcium when they eat it. Your turtles may not eat it right away either, but give it time, they have a natural taste for it.
Oh and get rid of the gravel. ( though I mentioned that in your other post)