Oh no
Did you test your water? Unfortunately some lfs get bad batches in which are riddled with parisites or disease or are suffering from ammonia poisoning from the tanks the fish shop keep them in. There was probably nothing you could do I know its no consollation x
And just to clarify, it's not necessary to have a male in the tank. I have a tank with 19 females and no males, and they get along just fine. I do think more females would help, as the bigger the group the less likely they are to hassle each other.
Ah so it turns out that whatever this guppy had gave it to 2 more of my guppies that just died. But I have been treating and all seems okay now...I have got 12+ little ones swimming around now...I cannot get pictures now as I am on vacation but I will try and post some when I get back