That space
is rather tight.
You say 75sqft, so 8x10? ...looks more like 6x8 if that red door is 24".
Maybe double check this?
There are no hard numbers that really work, too many variables, but the 4/10 rule is a good place to start...but IMO it's a
minimum, especially in harsh winter climates where they may not venture out much due to snow piling up.
Small foot prints(floor space) can be problematic in relation to height too,
the birds can't fly down from roost without crashing into something,
I see that might be an issue with this coop.
So
@Rosypetals, too small a space
might be the problem here.
Are all 8 of your birds the same age and raised together?
They are getting close to full sized so space is getting relatively smaller,
and onset of lay changes the dynamics of the pecking order
plus hormones flowing can up the drama and aggression.
Some birds are just more assertive, my wyandottes have always been that way.
More space or fewer birds could really help going into winter.
Climate is almost always a factor.
Please add your general geographical location to your profile.
It's easy to do, then it's always there!