There are some others who might chime in on this, but in general I wouldn't be too worried. Chapter publications reflect your expertise on a topic and won't be a substantial part of how your application was reviewed - esp. second authored ones. At the time of interview, if it comes up or you feel a need to bring it up, just discuss your interest/knowledge of the topics of the chapters and tell the story you described here. I don't this will cause much problem. We'll see what others say.