Poisonous concoction is doing half as much damage as it should

Poisonous concoction includes a "100 more magnitude of poison inflicted" modifier that is not being applied.

I compared the poison damage per second of Fulminating Concoction and Poisonous Concoction using the exact same support gems with Plaguefinger gloves, so all damage applies to poison magnitude. The poison damage per second of both abilities is roughly the same, where I would expect Poisonous Concoction to be about double.

I'm also certain this is not just a tooltip bug. I tested both concoctions on a boss and they were doing similar amounts of poison damage.

yes, how come the "leeching toxins" that increases poison magnitude has on effect on the "poisonous concoction" damage????