There was indeed a reason for all of them to be there still. After they separated from the twins' group, the experts went on hunting for Dark Green Cocoons. After all, they, too, noticed those lights were coming from them.
However, even though they passed by the sight of various Cocoons, they were all dead or dying. The lights themselves seemed to have no use they could think of. It wouldn't be a problem since it is believed a portal would appear once they were destroyed. Unfortunately, there were no portals left behind.
It was then that they noticed that the roots began to die as well, so they moved back to the crossing point to the next region. If the roots were dying, perhaps the killing roots near the border would die as well, right?
