I'm sorry you are having troubles! Are you sure this new fish is a Female?? Can you post pics for us? We'd need to see the anal fin.
This sounds like Male behavior... pestering the females... and possibly challenging other males.
What size tank is this? Molly's get big and every Molly I've had has had an attitude problem... I prefer Swordtails for that reason. Platies are more docile too. Tank size has a HUGE bearing on what to keep and who to keep together. Are some Molly species more bossy than others I wonder too!?
This sounds like Male behavior... pestering the females... and possibly challenging other males.
What size tank is this? Molly's get big and every Molly I've had has had an attitude problem... I prefer Swordtails for that reason. Platies are more docile too. Tank size has a HUGE bearing on what to keep and who to keep together. Are some Molly species more bossy than others I wonder too!?