I don't have suggestions, but I can certainly identify. I have two chickens. I hand raised them in the house. They did not even go outside until they were almost a year old. When they were about two, one of them (not the alpha hen) suddenly became very aggressive to me. One day she was fine, one day not. It got progressively worse. Now they are four years old, and this chicken will run, quickly, and pass food and water, just to attack me. She will peck my foot as hard as she can, she will approach me with her head high and sometimes jump up and try to scratch my leg.
It should be noted that she is NOT curious or just seeing if my foot is food. She is attacking me. She does not do this with my wife, or my son. And the other chicken doesn't do this either. This kills me. I love these chickens and yet I have no idea why suddenly one turned on me. I have been on these and other boards and gotten a number of suggestions. On those suggestions, I have taken the time to pick her up and carry her around for a few minutes a day for a few months with no change (even now, if I pick her up, she stops her aggression, assuming I can catch her). I have also tried to "peck" her back on suggestion. If she pecked me, I would hold her down and mock-peck her lightly with a finger. No difference.
So I can't help you, but I can say to many people trying to explain away this behavior as only perceived aggression that this is real aggression. I just don't know why or how to stop it.