GCC suddenly hates me??? :(

I've had my gcc for about a year, from what i was told he is about 3 years old now. He was very friendly and never bit anybody. Now all of the sudden, starting about 2 months ago, he will randomly hate me. Some days hes very nice to me. Other days, when i go over to his cage he gets all poofy and mad, makes weird noises and rocks back and forth if i touch him when hes acting like this i will get bit HARD. He will also knock down his food if im the one who puts it in his cage. The only changes i can think of since this started is, firstly, one day i was trying to put him back in his cage and when he was flying something happened to one of his feathers and it was out of place for a couple days. Im not sure if thats even relevant but maybe hes mad at me because of it. Next, about a month before this happened, i did put a mirror in his cage, not sure if thats relevant either. Lastly, about 4 months before this behavior started i got another bird, an african grey. I am the only one hes ever mean to, he likes everybody else. We used to be best friends, he was always on my shoulder and preening my hair.. now he just hates me sometimes.. i dont get it. Any advice would be greatly appreciated.

GET rid of the mirror!

He may hawe identified you as his mate, in which case, you'll be the object of his hormones/impulses/aggravations.
The only thing that has helped me (with Rickeybird the Terrible) is this.
Ever since the Rickeybird hit sexual maturity at about 3-4 years of age, I've had to manage his hormones! If kept on too steady a long day, and too much light, he stayed "in the mood" (aggressive, even louder than usual, pleasuring himself on my neck ) year round. If I keep him on a natural light schedule... up with dawn, down with dusk, year around... THEN he's only a little monster rooster from July to September). He has his own room, so I can do that easily.

I did take the mirror away about 2 weeks ago, no change in behavior