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Each breakout terminal has one GND port.
One pump per terminal.

The second pump would be connected in the same way as the first, only difference is this 2nd pump will be on the 2nd terminal.

Each BO box can individually control up to 2x 1-10v devices or pumps. For a 3rd pump, you would need a 2nd BO box.

The connection looks fine to me.

It would be best to run each pump on its own 1-10v channel, otherwise they will react to the same commands.