I have three Albino cories, and they would leave out the Emerald cory. He would swim near them and they would swim away. So I got another Emerald to up in a different tank and moved the one I had with the albinos, now they stay together.
Cories school best with matching cories. I'm of the opinion that you should have 6 or more of each type of cory you intend to have, even though they might not swim in tight schools--and many schooling fish don't unless they're insecure--they are still a social species that should be kept in a group or not at all.
Hopefully you can get some buddies for your loach soon.