Oh yeah don't use reverse ossmosis water. This could be part of the problem. Mist with distilled water and fill the water bowl(s) with either dechlorinated tap or spring water.
Clean out the tank and all its funiture with a bleach/water solution, about a 1:10 ratio. Rinse thoroughly and rinse with water with dechlorinator in it. Wooden items cannot be bleached, but you can boil or bake them. Plastic cannot be boiled or baked, but can be bleached.
Lastly get these guys to the vet.