The protection is greatest when speaking in the well of the House or on the floor of the Senate. It can extend to hearings held away from the Capitol, but there are limits. I think recording video for viral dissemination that is not a part of a Congressional function, especially when specifically citing the non-Congress credentials of the speakers as claims to authority, puts this in question. I do not think the Speech and Debate Clause of the Constitution applies. Others may differ.
I agree that the speech and debate exception may not technically apply. But I also don’t think their statements were technically illegal, so it doesn’t matter because they’ll be protected free speech anyway.