Toads and the newts cant go together. The newts need deep water as they like the swim, the toads only like a few inches (not more than where they can stretch their legs out and touch the bottom).
Toads need a few inches of water, little bit of land.
Newts need more than a few inches of water, and a little bite of land.
and the salamader...no way, the toads/newts are toxic and could kill the salamaner.
You need either all toads, all newts, and salamders.
What size tank? What kinda filtration? What kinda water/land set up?