Well, my cories are doing well -- I'm not sure if it was just hunger or what, but after a day or so the albino stopped being lethargic and is now friends with the newcomer

Since my tank is small, I think I will only be adding 1 more guppy, 1 more danio, and 1 more cory to keep everyone happy and in a group. We'll definitely be doing so gradually to make sure everything is going smoothly.

Thanks for all your help!