Thanks Guys for all your advice,
I have separated them but have just noticed one of the newer chickens has nasal discharge which probably means the other one will get it too (bang goes another £80 at the vet....hubby not happy!) and can't say I am looking forward to administering more injections, I had a meltdown at my vet when I had to give the injection for the first time. My older chickens are 3 and half and never had any health problems before, am wondering if the new chickens did bring it with them? They seemed bright and healthy.
Now I have separated them I am hoping they will go back together okay, that pecking order thing was horrible and swore I would never have new chickens again as it took 3 weeks. chickens are sooooo nasty! happy to say they are all friends now
Will keep you posted