I wouldn't put mollies of any kind in a 10 gallon. They produce lots of waste relative to their size and really need more room to swim than what a 10 gallon affords them. The tank is fully stocked IMO.
As an aside, I wanted to let you know how balloon fish are created so you can make an informed decision on whether you want to keep any in the future. Balloon fish are created from selectively breeding short bodied (deformed) fish together to exaggerate the deformity. This is a lot different to me than selective breeding to create color variants. The balloon bodied fish typically have more trouble swimming, are more susceptible to disease, and often have a shorter lifespan than their non-short bodied counterparts. It's basically a way that breeders/wholesalers have been able to make money off fish that should have been culls. I find it unethical, but that is JMO.