Responses
Unless I missed something, nothing was ever outright said, though it may have been hinted at that there once was something between Nick and Ash. As for the main story, Kyle was pissed at Ash due to his treatment of Karlyle. (Though I suspect one of the early "official" chapters might be missing pages, and maybe it was said there, idk ;p)
Nick dated ash prior to becoming a pair with Kyle. Their relationship is written in a prequel and that's also how ash and karlyle met but they didn't know each other if you get what I mean.
Was tryna re-read but i got lazy and i forgot but whats the drama between nick, ash, and kyle? cuz i remember in the story that something happened between nick and ash? not sure tho