Too many members leaving the server at the same time

Too many members leave the server at the same time, a total of 300 members left my server in 1 hour. I checked discord's audit log, no one kicked them. Our server is still working as usual so there is no reason for them to leave in bulk. I'm wondering what caused them to leave the server in such a mass. Is it a hack or a link installation? Additional info: this is server partner, we have more than 20 boosts, almost they join server using vanity link.