Birds can go thru adolesence. I have read that with Suns its around 2 years of age...so it is likely its being a bratty teenager. Be consistent and praise good behavior. Let them know who is boss without being agressive.
soft voices and stern looks...seriously... give them a dirty look and they react...something to do with how they react to each other in the wild... yelling or loud voices makes them think you are communicating-they like it. Dirty looks... i guess its like you just puffed up and attacked them ahhhaha.
good luck.