My flock has turned to the dark side, what is wrong?

[AkMartine]

About a month ago, I noticed that one of my red hens had a spot on her back near her tail with only underfeather fluffing out, like her normal red feathers were pecked away. It didn't change much for a while, and I know she is the bottom of the pecking order (she is one of four chickens I own), so I didn't think much of it. Then I noticed it happening to the other two chickens, the same strange bald underfeathers on their back, the top feathers plucked out.
But now it has gotten very bad, to the point that the dominant pecking chicken (one of two Australorps) has pecked out most of the other's feathers on their backs, necks and their fluffy bottoms, and the whole flock is skittery and afraid of me when they loved me so much before. What is going on? I have been very busy the past couple of months and haven't seen them as often as I normally do, could that be a contributing factor?
I feel like such a horrible mother to my chicks! Please help! I want my loving, adorable hens back!

 

[Nikitaa]

Im not sure whats causing this so I can't help there, sorry. But I do know there is a spray you can use on your birds that smells and tastes bad and stops chickens from pecking other chickens. I don't know how good it is because I plan tomorrow. But at least you can get the pecking stopped untill you work out why it started.

 

[spikennipper]

Can we see a photo of your chickens please?