No fertilization after root work, use of dilute fertilizer (then or any
other time) are all (IMHO) bonsai myths. NO ONE has managed to provide me with
the science behind any of them.
I routinely fertilize after repotting, and I always mix the fertilizer
according to the label, and have never had any
problems therefrom.

Is it possible that timing and strength of fertilizer may be influenced by
climate & seasons? What is appropriate in Florida in the summer may be
overfeeding in Toronto in the fall.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)