The ladies need a MAN!?!

I have 16 ladies (14 months old) who all of a sudden undergone some strange flock behavior. They had been raised with a rooster and he did a pretty good job keeping things under control...except he wasn't too fond of us human types. Tried all sorts of things, but he had to go. The rooster has been gone about 7 weeks now and now the alpha hen is acting like a rooster, but very aggressive with the other hens. Most of the other ladies are developing bare patches in the back of their heads and the back feathers are going to pot. The strange thing is, when she mounts another hen, two or three others will join in and peck the heck out of the poor victim. It is brutal to observe. I have seen it twice today. They seem to love picking on the lowest on the totem pole. Last week my lowest ranking hen was found dead in the coop. After observing today's behavior I am wondering if they killed her.
The ladies are healthy, dewormed recently, nothing out of the ordinary. Plenty of room in the coop, 40x40 run....
I am absolutely baffled by this behavior. Is this normal flock dynamics? Or is it a phenomenon of a flock that had a roo, that has a roo no more? I have a replacement roo, but he is only 7 weeks old. It will be quite some time before he is ready to fill his role.
I see lots of pics of other people's flocks here on BYC and they all look so beautiful and have no feathers missing or bald heads. Right now, my ladies are in worse shape than they were before with mean ol Mr Nasty around. He could be rough with them, but the hens are absolutely brutal to one another.
Do I step in? With what? Pinless peepers?
Any else ever experience this?