I have noticed that you tend to focus most on Nick even in your group stories, but there's nothing wrong with that. In fact, I bet the majority of readers prefer it that way. We all probably have that one guy that we tend to center our stories on, and not necessarily because he's our favorite. Nick's not my favorite either, but I have written more stories centered on him in the last decade than I have any of the other guys. He's just fun to write about and makes for an interesting character.
As far as recycling storylines goes, I do it too. I don't set out to, but I've noticed it's become sort of a pattern with the novels I've started writing in the past few years. Almost all of them could be seen as recycled versions of my older stories if you look at just the basic premise. Maybe that is just what happens when you run out of ideas; you start recycling the old ones LOL. The reason it doesn't bother me is that I feel like I am improving upon my old writing that way, by taking an old premise and putting a new spin on it, writing it better than I did the first (or second, in some cases LOL) time around. It's never the same story twice, even if the storylines are similar.