Looking good, and yea that loner will eventually find the shells. Even though they might look kinda spooked now, once settled they'll swim all around the tank (at least that was my experience, the first week they didn't leave the shells at all, I had to do extra wc's just to suck up all the uneaten food around them, now they're all over picking all the food up).
I'd also suggest you spread out the shells more, won't see as much aggression this way.