Conduit only attacks one mob at a time

I built a full conduit at the front of an ocean monument, where guardians were oddly aggregating in, seeing if I could farm their drops that way. But I noticed that only one guardian is being attacked by the conduit at a time. I am unable to see multiple guardians being attacked by the same conduit (even though I built another full conduit earlier under the center of the monument, its attack range does not overlap with the conduit I built at the front)

The third guardian from the bottom left being the conduit's target.

The left guardian being killed by the Conduit's attack; the Guardian on the right is about to be attacked.

F3 Debug screen