I agree with Michael...
I think the cage sharing could be the problem with your Meyers.
I have a Meyers too, very close to the same age, and I can't
even IMAGINE him sharing a cage with any other bird.
He'd have a FIT!
My bird has also begun to get aggressive towards my other two
parrots - who are MUCH larger than he is - and won't play
nicely on cage tops or playstands with them at all.
It's gotten so bad, that I'm afraid for his safety should one
of the bigger parrots get fed up with his 'tude and really
bite the heck out of him! I'm also worried that he could
very well hurt one of them by biting toes or pecking an eye.
I've had my Meyers now for a year next month. He was never
the ONLY bird here, but he sure acts like he *should be*...!