One can have multiple accounts, even more than 100 accounts, the forum have no such rules to have only one account. But there are some community standard which are like
You can not join same signature with multiple account
You can not send merit to your alt accounts
You can not join with multi account from a signature and many more.

Have any of the account done such offense? If they did then we can tell they were cheating, otherwise all good.
[Sorry, my tor is too slow to load images]

Could it be a group who worked together?