Possibly an insect hatch in that area. if the pond bottom is different such as one area has plants, gravel, sand or depth you can have an insect hatch in one area. My trout were very predictable but insect hatches did sometimes change their routine. Just a thought.
I think this is a very likely possibility. My trout seem pretty keyed in on feeding on the surface, and I think some insects on the surface might have attracted them. There was a lot of activity in the corner where they moved to. Most have moved back to the regular feeding area, which is good since the water temperatures have warmed and they are eating really well now.
