I would go get me one more of each! Your coop sounds like it will serve them. Then nobody will be left without someone of their kind.I was told plymouth rocks need 15sqft each outside and are very territorial. I could see if the feed store has more chicks still. My run has a roof. I had ducks previous and they liked their SPACE. I had the 2 story "coop" which is a coop-run and the rabbit hutch. They both went into the 8footx8foot wire enclosure. it's got a hardware cloth bottom (till 4 feet) then it's double chicken wire on top and otherwise. The ducks had a 30x30 semi-free range with a pond and then when I was home they had my 3 acres, 1/2 acre of which is cleared. Most summer days they were atleast in the semi-free range, if not totally free range.
I'm in the upper part of the mid New England states...
I had both in my flocks. Kinda thought I prefer the BR but the red (who knows if it's really RIR or production) will lay way more eggs and eat less feed than the BR. One reason I don't like having all the same breeds is I like getting different color eggs and having a variety of eye candy in my yard. Being able to tell them apart helps if they show any health conditions. Same for eggs.
My Feb born BR started laying on the 4th of July last year. My June born girls (different breeds) are barely starting to lay this past month. I also wouldn't get later born chicks if I could avoid it. Because now my ones that barely started laying will still molt this fall. So less over all eggs. However, my girls that lay later do start with more full sized than pullet sized eggs.
I don't find my barred rock to be any more territorial than any other chicken. There is a pecking order and all will follow it. Reds can hold their on with rocks!