No idea why this is happening. In the first image, I placed and activated four blocks of TNT, one for each flower (The accelerator is just there to show the particles easier). Each flower got one TNT to generate mana.
In the second image, however, all three placed TNT went into a single flower, somehow without overflowing. Verified with the Wand of the Forest, only one Entropynnium in that setup had Mana.
TNT in both cases was placed by hand on the redstone blocks as fast as I could. Breaking the Entropynniums and replacing them did not change this.
HOWEVER: placing an additional TNT blew it up, so it seems that the other two flowers are acting as if they contain mana when actually they do not. There was only a single normal Mana Spreader.