Strange behavior...

Hi. I'm in Connecticut and have been longingly looking at my pond through
the windows for months now. On the warmer days I'd see the fish swimming
around, and then there was that spell that the ice was so thick I thought
spring would never come! I don't know why, but the water seems more
green this year than it has in any previous years. But that's not my
problem: Yesterday when I was home for lunch I was, as usual, looking out
the window at the pond, and noticed my big platinum koi acting kind of
frisky. He was swimming fast around the perimeter, and even did a little
jump. I thought "spawning?" but no, it's too early. I looked away for a
few minutes and when I came back, I didn't see him, but I did see a lot of
splashing going on from a point where I keep some potted plants on a ledge.
I figured he was still playing and feeling frisky and was trying to knock
over a plant. This morning before work I did not see him, and at lunch
(now) I couldn't see him, either. I took a walk out there (not a wise idea
in office attire - there's so much mud from this horrible winter!) and
found that he was trapped behind the potted plant! Not only that, but
there were 4 five others trapped, too! (one dead)

What in heck possessed them to all go back there and get stuck all of a
sudden? That plant has been there in that same place for years, why this
year, and why all of them? I am totally stumped as to what caused them to
all of a sudden find that area so appealing that they got themselves stuck -
any thoughts?????
Thanks in advance.
Sue