a total newbie and I need help

We purchased four birds from a local chicken enthusiast. She shows her ladies and the girls we got have been very pampered and loved. We purchased two 1 year old girls, a black Australorp and a buff orpington. They are big, beautiful and very sweet to us. They were housed with bantams and silkies. We also purchased two frizzle serama's that are about 4 months old, they were housed with Maran pullets/cockerals on the same farm. I asked the ladies that we purchased them off of if they think that the two bigs would be good to the littles in the same coop and they thought they would, seeing as they were used to being around the bantams without issue... WELL, issue. We got them this past Friday and they spent Saturday inspecting the coop and generally calming down. Sunday was very stressful as they began figuring out their pecking order. This is where the problem begins. I have a very dominate serama and a dominate Australorp. On Sunday it gave us a chuckle to see this teeny tiny serama puff its neck and chest make its tiny peep charge call and start charging our big and beautiful black australorp. The fighting got more intense with our little serama losing most of her head feathers. I've read not to intervene so we kept our distance but made sure that the littles were getting food and water as "the boss" was not sharing. I came home from work yesterday and couldn't take it anymore, the once dominate serama was completely submitted, tucked in a corner with her head shoved downward and the bigs would peck her bottom so she would start running away then they would chase her. I noticed then that her poor head (now bald) was very red. no blood, just red but there was red tinting (as though she had been bleeding) on her neck feathers. I intervened right away. When I took the one serama out to put her in the box the other came running out crying too (they had both been being chased, one worse then the other) I set both of them up in a bit of a rehab center, both of their combs (one was pink and the other a light red) had turned to a more flash toned peach, I gave the badly bald one a bath and rubbed some antibiotic ointment on her head (she loved the special treatment and kept cooing and closing her eyes) Her favorite was the hair dryer. I plan to keep them separate until they are both back to full health (feathers in tact!) but I don't know if I should put them back in with them or build a separate coop...One for the bigs, one for the littles.... any advise is greatly appreciated. We do plan on building onto the run for the coop that we have, as the one it came with is pretty small.... i also plan to put nesting box curtain up... I just don't know, I love my tiny frizzles and don't want to see them hurt. I also love my big girls and don't want to see them be such bullies....

 

thanks you two for the advice it is much appreciated! I think separate coops is the way to go too... My hubby and I are going to both come up with plans and sit down to discuss tonight. I don't want my girls to stress and I think two separate coops with maybe side by side runs will help, and like Dekel said, maybe one day we can open the runs up and there will be harmony...We'll have some time as I think my little's will be in rehab for awhile regrowing their poor feathers... ugh