Re-introduction of chicks to flock

Here's my situation: I have nine 3-week old chicks. Five days ago, I had to remove 2 chicks from the group because their backsides were getting pecked raw by the others. I covered the wounds in blue-kote and the 2 are now completely recovered. I attempted to reintroduce them to the other 7 this morning and they were immediately assaulted. How do I get these 2 successfully re-introduced to the rest of my flock? Thanks for the help.