How to improve my Terrarium?

So this is my current terrarium, an ExoTerra 45x45x60, with a custom stirofoam background and the soil is a mixture of plantation soil and musk from ExoTerra.
My other plants died recently, two of excess water and one dried up, all in a weeks time... leaving me with one real plant upfront, two fakes high on the back.

My challenge: how exactly would you make this perfect for my two Gargs? I think they have been living pretty happily, they eat their repashy, grow, poo and show their colors; but it can be better!
Exact ideas on how, please

Thanks