It seems like one of my hens has been ostracized by the other 3?

[Youngchics]

i used to get worried when my chickens did that. (my chicks STILL do that) they are 7 or so months old now. yours sounds like an intense pecking order. but don't worry, uness the poor hen starts getting really hurt, like @aart said before. post again if it gets worse, or if entire clumps (or just little clumps) of feathers starts being pulled. but currently it sounds fine. if you could post a video or picture of the hen getting attacked, that might help to see how intense. it will happen again.

I am having the same problem with 3 of my 5hens picking on the one named Nugget. To the point ox not letting her eat or drink. She seems cone health wise. They even keep her out of the dusting box. ????
Eat

 

[Old Lady 5301]

This sounds similar to what is going on with my hens. But no mounting behavior. It has been 6 days that they are staying separate, no signs of illness or injury. Sassy, the hen being ostracized is a rir and the rest are a cross with rir.( They have golden coloring on their feathers). They don't free range, too many feral cats in the neighborhood and no rooster. Sassy only seems to come out of the coop when I am present.