It appears that your flock is teaching new members the chicken attack behavior. One method that might help in your situation is to closely observe them and remove the ringleaders.
Guineas are delicious.
I brood my guinea keets only with other guinea keets. My guineas are housed in a separate coop of their own.
My guineas are also a large enough flock (14) that they can have proper flock dynamics. The free range are where they can and have been in at the same time as the chickens and turkeys...
If you brood and house them separately, they will leave your chickens alone. I can allow my guineas, chickens and turkeys to free range in the same area at the same time and each group will keep to themselves.
Guinea keets brooded with chicks and raised with chickens will imprint and lose the...