I have to agree that you are way overstocked for a 29 gallon tank and the tang really needs a lot bigger tank to stay healthy.
I would suggest slowing down and asking alot of questions and research before you set yourself up to fail. The tang really needs 4 foot tank with best being 5+ in legnth. if not they develope HLLE and can die quickly from it among many other things.
something else is that you dont need to have trhe damsels to cycle the tank you can just throw in a piece of shrimp from the store to cycle it out.
Mike