I have observed this joint inflation/deflation response before between haddonis and giganteas, but with no other two clown anemone species.
In addition to infection, the one other possible explanation may be due to stress chemicals and/or spawning. When anemones are badly stressed, they spawn. In the case of a small anemone spawning at night, you may not even be aware it has happened. However haddonis and giganteas may be closely related enough that the chemical triggers in the water cause the same synchronous spawning behavior that it does in the wild. The haddoni may have spawned the first night, and may be continuing to try to spawn every night as long as the chemical triggers are present(?) Just a thought...