Hey 
RESQME49 
Sorry, I just want to make sure I am interpreting this correctly, you currently have 7 chickens in a 6 x 4 coop with a 4 x 8 run?  A 6 x 4 coop is suitable for 6 fully grown large chickens and a 4 x 8 run, 3 fully grown large chickens.  If my calculations are right, yep, get started on those extensions 
However, even at 14 x 4 on the run, that is suitable for 5 to 6 chickens.
Rule of thumb is 4 square foot of coop space per LF [large fowl] and 10 square foot of run [but you can skimp on that a little if they are free ranging for most of the time which I see you plan to do].
Living in Aus, I am not familiar with the 'Original Chicken Man' but most prefab chicken coops only house half the number of chickens they advertise they accommodate.
Also, you had the original 4 a few days before you added 3 more?  Did you quarantine the newbies or just pop them in the coop/run when you got them?
If you just popped them in, there are going to be squabbles while the pecking order reorganises itself and you are probably lucky that you have not witnessed any actual fighting which may be due to the RIR and Sexlinks not having been in the coop and run very long themselves.
When introducing chickens, it is best to keep them separated via a ‘look but not touch’ method for a couple of weeks so that they can get used to each other before introduction.  I have seen some nasty injuries here on BYC from chickens just being popped in without a proper introduction.
Anyhow, as they are not actually fighting, no one is getting hurt and they have already been together for a couple of days, you are probably safe leaving them now and just keeping an eye on them while the pecking order sorts itself out.  Definitely look at getting them some more room though.
Keeping in mind that recommended roost space for each LF is 2 foot, are you certain there is “plenty of room up there”?  The browns may not be roosting because they are being picked on and the quarters are too close.
None of this is meant to be harsh or a criticism, hopefully just some helpful pointers for ensuring your girls are happy.  Confined quarters can also lead to feather picking and boredom etc.
Topic of the Week - Adding New Chickens to the Flock.
Good luck and best wishes!
Edited to fix up some and's and are's in the wrong place and other bits that did not make sense 
