Sounds to me like your maturing flock is working out their pecking order, plus it's summer/breeding season and the males' hormones are kicking in X10 (which usually surfaces as aggression in my flocks). Your 2 low birds are overly sensitive about it/traumatized from it since this is their first experience with it (some get used to it and learn to cope, some don't). My Guineas do get pretty traumatized after fights and will mope around and be very submissive to their aggressors for a while. It's basically the nature of the pecking order beast, and typical that 1 or 2 birds end up ostracized from the flock. You will see most likely this behavior every breeding season from here on out and as time passes you will see that it's not always the same birds that get picked on, or the same birds that are the aggressors. Free ranging them all as much as possible helps everybody burn off their extra energy and aggression, plus it gives the 2 ostracized birds more room to get away from being attacked/picked on.
Over the years I've had Guineas I have had quite a few birds that get picked on hang back from the rest and refuse to coop up for a while... sometimes it passes, sometimes the low birds learn to dodge the blows and keep their distance but still remain near the flock. Sometimes it doesn't get any worse after the initial attack, but sometimes it gets so bad to the point that the ostracized/picked on bird or birds have bloody wounds and have to be caged (always near the flock tho) until their wounds are healed... but sometimes I have had to merge the picked on birds into other flocks (which isn't a big deal for me because I have 5 flocks and one usually consists of younger birds). I have even had to re-home some of my males/bullies (or send them to freezer camp) because they were too relentless with their bullying and continued to cause too much turmoil in the flock and in the coop/pen. I've also had instances where the low bird or birds have been pushed so far away from the flock that they've been nabbed by predators because they did not have the safety of the flock "watching their backs". So you'll want to keep an eye on the 2 ostracized birds and make sure they do not get ran off too far.
Typically it's just 1 or 2 males that initiate picking on the low bird or birds (and then the others in the flock follow suit... monkey see, monkey do) so if you can, keep an eye on the flock and see if you can figure out who starts it. With the 2 birds already ostracized, the aggressors' next target may be your chickens... so if you can figure out exactly who starts it (like I said, usually males) and separate the bullies for a week or so that may give the bullies an effective attitude adjustment while giving the other 2 birds a chance to settle back into the rest of the flock. If you don't have a separate pen or large cage for the bullies, then the large wire dog crates work well for this too.
After the weather cools down the hormone levels drop back to normal and then there's minimal scuffling in my flocks, hopefully that's how things work out with your flock as well. Welcome to the joys of owning Guineas.
