I dont know what to do

Do they do this in the run or are they picking on the others when they are in the coop too?

When I merged my 5 girls (3 EE & 2 Light Brahma's) with my original 10 (they are only 2 & 4 weeks apart in age), I had to fence off an area in the run, just for the 5 little ones, because the older 10 were so mean to them. I used a roll of hardware cloth and blocked off an area, so they could see each other, but where the 5 were still safe. 3 weeks later, I opened one side of the fenced off area, so that the 5 could go out with the others, but could go back to the safety of their fenced area. The older ones never intruded into the fenced off area.

At night, the 5 younger were still being housed in a large rubbermaid container, and I did this for 2 weeks, then took it out to see what would happen. The younger 5 found the roost & stayed up there, the older 10 were still puppy piling in the corner of the coop. 2 weeks went by before the older 10 joined the 5 on the roost. But the younger 5 would huddle on a corner, because they would still get pecked from time to time. Never had blood or feather loss, but a few squawks & screeches from time to time.

Even now (they were merged 4th of July weekend), the 10 stay separate from the 5 younger. The 5 younger go to bed first, and are the last to leave the coop in the morning.

How long have they been together?

 

Chicken jail. You can use a dog carrier or some other smallish makeshift pen or cage. Put it where the others can see them. Three or four days of this might help. Or you may have to separate them and put each one in a cage by herself. Little bullies!

 

If they are attacking you, they are way too aggressive for my taste and would find their way to the freezer or on there way to Craigslist or something. (of course you would want to disclose their bad attitudes to a new person) But if you want to try and keep them, I would get a large dog crate and keep them or the top two of the three in there for a few days. If you have the ability to do as Mommy 2 Wee Ones suggested, that is perfect too. But the idea is to separate them, put them in a "time out" so to say. Keep them where the others can see them. After a few days, try and re-introduce them. See how it goes. They are always going to go through the pecking order squables at first, but drawing blood, terrorizing and attacking humans is a bit excessive. I hope you can find a solution that works for you.

 

If they're 20 weeks old, are you sure that they are hens? I don't know about the breed, but their behavior sounds like juvenile roos. I'm a newbie, and have been reading a lot--don't recall hens attacking humans.