Blood Hunter: when Crimson Rite is active is it a once per round?

I’m confused on blood hunter. When crimson rite is active is it a once per round or is it constant and if so do you keep losing HP per round or one time HP loss Once active, the extra damage is added each attack that hits for as long as it’s active. The HP damage/reduction only occurs upon activating it. Once the rite is dropped, the max HP loss returns (but the damage remains).

— Matthew Mercer (@matthewmercer) January 17, 2018

Does it work on a bow, or other launchers? I’d hope so, since Archery style is available for Blood Hunters. It does indeed, and the damage benefit carries to the ammunition long enough for impact

— Matthew Mercer (@matthewmercer) January 17, 2018