Vitamin supplements

I had a recent experience which I want to share.  I introduced a
green spotted puffer into my 45high tank to reduce the pond snail
infestation to manageable proportions.  After a few days, I realized that
this was a bad move for the sake of my angelfish, who were losing ventral
fins at an alarming rate.  I yanked the puffer, and began to treat my fish
with vita-chem to help them regenerate their fins.  I initially avoided
dosing the entire tank, preferring to supplement the food and maximize the
vitamin uptake.  I had to leave town for a week, however, and decided to
dose the tank for the week I would be gone, since the fish wouldn't be

Now for the APD-relevant part.  Many of the older leaves on my marble
queen sword and much of the valisneria began to act like they had been
burned by a fertilizer.  The leaves turned brown and began to decompose.
Fortunately, the plants were really healthy (in this tank at least :->)
and are in no danger of dying completely.  The fish are ok as well.
Anyone have any similar experiences?