Separating Budgies

I am trying to tame my budgie kiwi and its not going as planned. Kiwi is kept with another bird, Frosty who is so timid that I can't touch the cage without a fit. So anyways I get kiwi tame then he hangs out with frosty and BAM the next day he is terrified of me, and Frosty make a MESS with his seed so now their are mice... 

I was thinking of rehoming Frosty since he doesn't fit in the flock, but him and Kiwi are bonded and yeah...