Feathers missing on wings only, one chicken puffed up and not eating

My chickens have recently been losing feathers on one area of their wings. 4 of our 6 chickens have been affected by this, and 2 of them have been pecked in these places to cause bleeding. I have tried putting lice and mite powder in their sand, coop and on the chickens directly, but the problem is not getting any better.

Here are some images of their wings. Sorry for the poor quality, I can take more pictures if necessary. Some of their wings are purple as I put violet spray on their wounds to stop them being pecked.

http://imgur.com/a/yMfLb

Another problem that may be linked is that one of the chickens (that has not had their wing pecked) has as of this morning been puffed up, drinking a lot of water and standing around doing nothing. There was some diarrhea in the coop this morning which I can only assume was hers. She is the chicken in the last 4 images in the album that I posted above. Does this sound like any illness you know of? And how do I treat it? Thank you.

Here are some images of her vent. It appears that there is some egg there, but I'm not sure what it is and I don't want to try to remove it and end up doing more harm than good.

http://imgur.com/a/ftGg9

, sorry for the circumstances. It appears to me that it is very likely that the two birds that are fully feathered are feather plucking and picking at the other four. When birds are confined during the winter they become bored and frequently develop bad habits. Pin-Less Peepers can frequently help in breaking this habit.

The bird in the second picture was laying a soft shelled egg which broke internally. This may very well be an indication of serious laying problems.