So my spouse and I got this little blue and white budgie last summer who we named Sir Erik to add to our flock of budgies (five at the time) and everything was fine he grew close to our second oldest Avo. However I left to visit my parents and work for a couple months. I come back to a heated battle: Sir Erik and our eldest Putte had split the cage into two groups with Sir Erik driving the poor old bird out of his cage every morning since my return. It got worse two days ago when a member of putte's group died of cancer. My spouse has already tried putting Sir Erik in his own cage but he got so depressed he wasn't eating at all. So we thought adding a new bird might help which it sort of did but not really. (Side note: Sir Erik is the trouble maker not Putte who has tried to become friends with him many times only to be cursed at and pecked) So the question is how do we stop this without separating the one?
Sir Eric has probably gotten very close to you and the way you care for him so when you left he started to miss you and decided to punish Putte for it. The best thing you can do is probably to show Sir Eric some special attention and slowly re-introduce him to Putte. I hope this was helpful!