It could be that the move was harsh, the water switch too much so he is very stressed.
I know of two cases where a large paroon perished after going from being very long term in bad water to good. So this can happen. At least on the surface, it looked like that.
It could be that he hit the glass so hard in your tank that his eyes got cloudy. Cloudy eyes can be due to poor water as well as bacterial infection too.
The whiteness is strange. Not a normal symptom unless a picture can clarify what you mean.
Stunting does not prevent growth but diminishes the max size. He might grow to 3' instead of 5' and might do so quicker than normal (the growth "energy" suppressed before may be released explosively).
FYI, paroons are very highly predatory, unlike IDS. If he survives and thrives, he will destroy your current stock, chances are.