I am sure things will go back to normal, it is true that three of your budgies didn't want to train, but the fact that Pippin wanted so bad to train and Maru accepted to train too (even if his results weren't as positive as you expected, I guess) is a good sign!
I have started to read your thread from the start, and I'm not even halfway,
but it is really interesting to read about the training sessions and the flock dynamics, and the videos of your budgies performing the tricks are awesome!
For now, the most interesting trick between yours for me is "pick up" the cat toy ball, mostly because this is the only one my budgie Celeste might be able to do out of all of them.
I have also read your fourth to last post where you said that the cat toy ball was a victim of "where in the world did I put it"... tell me about it.
I had a little toy soccer ball that would have been perfect for a trick I saw on YouTube, in which a budgie has to push it into the goal. However, I lost it. I have seen it a thousand times around the house, and now that I need it... it has disappeared.
Well, I haven't taught anything to Celeste except for touching the target yet, so it will take a lot of time to get to the tricks with a toy ball, but still...