Is forgiving colleagues for the extra amounts taken from them as a gift sufficient expiation for the sin after realizing that the transaction was usurious?

Lending with interest is usurious and forbidden. The one who engages in it must repent and feel remorse, for both are sinful. The Prophet, peace and blessings be upon him, cursed the one who consumes usury and the one who feeds it. The increases taken by the lender are not rightfully theirs. However, what was received before knowing the ruling or out of ignorance of its prohibition is forgiven. As for what remains outstanding, it is waived, based on the Almighty's saying: "And if you repent, you may have your principal – [thus] you do no wrong, nor are you wronged."