Well i got 2 full grown peppared and they always stay toghether and i have like 5 albinos but all of them are very small are they too young to school all 5 are like 0.75-1.25 inches big is it not in there small tiny brain yet?
Maybe you need a few more. They do best in groups of atleast 7. Your tank is pretty big, so they may have to grow a little bit before they chill together. Since they're so small, they may have to look for each other to school. Give them some time to get bigger, add a few more corys and I'm sure they'll school.