Just a thought about Monsta X MV...
I think the title ‘All In’ is really inmportant when it comes to tying together the flowers, the odd ritual (where Jooheon makes for a lovely witch doctor).
My theory is the flowers are probably poison, and the scenes in the MV may not be in order.
From the look of the flowers I think they are probably . Delphinium or Larkspur: Def- All parts of the plant contains alkaloid delphinine toxins causes vomiting and death both in humans and animals. It has cardiotoxic and neuromuscular blocking effects.
The neuromuscular blocking effects I think really come into play when the flower is fed to Hyungwon. He is beaten up and clearly in pain, now if a minor amount of this flower was ingested it more than likely will not kill you but it could block your pain sensors, allowing them to take him out of the 'warzone’ and him not feelings a thing.
The 'ritual’ scene you see them boiling down the flowers, this would more than likely make the poisons morr concentrated than eating just a flower.
With the title 'All In’ I think they made a brotherhood oath to carry through their rebellion until the end. The posion is used an an opt out option. If they are captured they can kill themselves and not allow themselves to be stripped of their goal and youth.
We see Shownu take the poison and Minhyuk pouring what I guess to be Hyungwon’s portion into the bath water and probably taking his own and dying in a very Romeo and Juleit style.
This is all I can say for the flowers and their possible significance.
PS. I think presenting the flower to the police was a way of saying “we will riot and cause you pain, but as a sign of mercy you can take this and not feel a thing”