Ok sorry for taking so long to respond...work life lol. So my run is 7x3 with the coop above it. I can’t remember the specifics for the coop. I can move some stuff around to create a couple obstacles after checking it out this morning. HOWEVER 2 of the 3 older chickens are bantams who are actually a little smaller than the newbies so I’m not sure how much protection obstacles will offer since those two can chase them anywhere. I don’t have a huge run because I put them into my enclosed garden almost daily. They get along pretty well in the garden it’s only in the run/coop we have an issue. And I don’t have any males, not allowed to where I live
7x3 is very tiny, especially for the number of birds you have, even if a couple are bantams. Around 50 sq ft would be the minimum to aim for, optimally more, as integration takes more space as you've seen. Part of the problem isn't just the overall sq footage, it's also the fact that it's narrow which makes it even more impossible for birds to put space between each other and I can see why you'd have problems adding obstacles. It makes sense they'd get along in the garden where there'd be more room and probably some obstacles too to keep the peace.
Is there any way of expanding the run area that they can use during the day? Possibly the coop too, though that might be harder depending on how it's built. Photos might help if you're not sure how you can expand. While it's nice that they can have some time outside of that, if it's not accessible most/all the time, it's not enough, especially when you're already having tension issues.