I'm afraid not. To be honest, you need to remove some fish.
Mollies and platies are too big for a 6.5 gallon tank. Platies need a tank with at least a 24 x 12 inch footprint while mollies need a 36 x 12 inch footprint.
You might get away with guppies, they need 18 x 12 inch footprint. Since the guppy you already have is male, I would try to exchange the molly and platy for a couple more male guppies. No females though or the tank would be grossly overpopulated in a month or two with guppy fry.
Can I check - is your tap water hard or soft? Livebearers need hard water and will suffer if kept in soft water. If you do have soft water it would be better to exchange them for one of the soft water nano fish.