I have just re-read the first post, and in that you say you have balloon mollies already and are intending to get a betta.
Mollies need hard water. Your tap water is perfect for them but if the tank really is 9 dH, that is far too soft.
One other thought has just occurred to me - do you use a water softener in the house? If you do, is the high GH from a bypass tap and the tank filled with 'softened' water?
Mollies need hard water. Your tap water is perfect for them but if the tank really is 9 dH, that is far too soft.
One other thought has just occurred to me - do you use a water softener in the house? If you do, is the high GH from a bypass tap and the tank filled with 'softened' water?