Pretty much normal behavior for a small number of guineas forced to live in close quarters with chickens. Guineas are a flock bird and do best when kept with at least a minimum of 10 guineas. They do not have the same mannerisms as chickens and only other guineas understand their behavior. When kept with lots of room and enough other guineas they will tend to keep to their own kind. They can even ostracize other guineas if they are a different color than the rest of them.
That you have not seen the guinea cock mate with the guinea hen is normal. The guinea breeding act occurs very quickly (hit and run) and is seldom seen except by very vigilant owners.
I raised guineas housed with chickens and turkeys. Because of the stress that the guineas put on all the rest of the poultry, I now house my guineas separately. I can free range the guineas, turkeys and chickens all at the same time in the same area without any problems. The guineas keep to themselves.
R2elk: Question for you, given your comment that guineas "can even ostracize other guineas if they are a different color than the rest of them." I have 5 guineas, 2 males and 3 females. One of the males is all white (White African guinea), and I have 2 female pearl grays and 1 male/1 female Royal Purple guinea. A few weeks ago, the female royal purple guinea was sort of ostracized by the others: they wouldn't let her eat or drink near them and she took to wandering away to herself. TODAY, when I went out to the guinea yard I was shocked that the other four guineas were all pecking at the White African male guinea, who up till now was sort of a leader of the whole group. I even saw blood on his neck, and between running away from them and crouching in a submissive hunch, I finally caught him up and separated him from them to let him heal in a separate area of his own.
My question is, do you think this guinea can be re-introduced to the rest of the flock? Is this some kind of mating behavior, or what? Any advice appreciated.