The current Senior Crew would have known, but their memories have clearly been altered. Amalthea is at least slightly aware of this, and they had a meeting about it during the beginning of the week after they all experienced the headaches Eunhyuk mentioned.

[but scien waves a hand]

Until we find the plants in question, we don't need to jump to conclusions. Flowers are relevant in a few situations, but none of them are lotuses or lycorises like we've seen.

The poison afflicted Hans through a flower's thorn. The symptoms of the poison were at first mild, like a cold, and then death overnight. It may be relevant to the Busybody and his sudden demise but even then the symptoms don't align. It likely is not relevant to those who are losing control of their violent urges on Thursdays.