Yes it is the cage. You must fix it ASAP before it turns out to be the lizards too.
Believe us.
I'be been in your shoes and I have killed Green Tree Monitors before. Because of wrong caging.
You can search for some older posts of mine here and you'll see. There are plenty of interesting discussions.
Cut this saline solution. Mist them with water if you want to, but that alone is not going to solve.
One last thing: they go bad FAST.

