They are delicate with watering aspects.
Gum tree takes very little bit of water, sometimes during hot summer of 2-3 months without rain some specimens of gum shut it self down.
At that stage it appear as if tree is dying, they most of the time come back.
I have 3 of them, still young samples from collected from the forest.

You may try burning one branch or two with the flame and wait to see what will happen after few months.
After quick fire, gum in the forest regenerate it self with the new branches in the affected area.
Just last week I drove along the fire affected forest and it is amassing to see a tree completely burned with one week old growth all over the branch.

I'm just testing this theory let me know if it works.

Peter