Alexander Wolfe, Marcel Barthel, and Roderick Strong were among the names at Worlds Collide. At RAW, it was Samoa Joe, Rey Mysterio, and Riddick Moss.
While injuries obviously happen, the amount within three days (as well as the similarity) was called, "unusual." It was unknown how all six happened, or the severity. Dave Meltzer noted all of them weren't concussed, but we'll know soon based on how quickly they return to the ring.
At Worlds Collide, Imperium defeated Undisputed Era, in this match three of the eight Superstars were dinged up. Wolfe took a kick to the face by Bobby Fish (seen below) and had to be removed from the match. He later tweeted out he was "fine."
As noted, Joe was removed from his match on RAW after going for a dive and then grabbing the back of his head. Rey Mysterio took on a MVP that night, and Riddick Moss made his main roster debut, alongside WWE 24/7 Champion Mojo Rawley. Meltzer said he wasn't sure what happened to cause Moss to get shaken up.