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is it ok to feed a baby RES , tuna fish, boiled white chicken, boiled egg whites???

Yes, these are ok, but should be considered a treat, and not fed more than once a month. Also make sure your baby RES is eating his veggies

what kind of veggies do they eat and dont eat

There's a "what to feed" and a "what not to feed" sticky at the top of this section of the forum. There's also more comprehensive lists on the nutrition section on redearslider.com

Veggies, it'll depend on your turtle. Most of the turtles have a preference towards certain veggies. It's good to start out with some lettuces and carrots, most turtle enjoy those a lot, and then branch off.