Ding ding ding... Linda got it right. drop the mollies and go with something else. Mollies might survive for a while but without a good amount of salt in the water and moderate to high PH they will not survive long term. They are also mostly vegitarian in their eating habits.
Has nothing to do with genetics.
10 gallons a week is plenty for the stock that you have. Unless you are trying to grow fish out or keep a huge amount of fish I wouldn't bother with more.
Yes, a lot of pet stores don't mention that mollies are brackish. I had some in a divided tank with bettas. They did okay for a while, then just croaked one night with no real sign of illness.
Ah I see, I've heard they are brackish but I've been told fresh water is ok for them. I guess I'll just wait for them all to die then since cories don't like salt. I just got some upside down catfish today. The restock has begun lol