It appears to be over eating. The fish is not really breathing heavily but fish do need to pump water over their gills which means that the mouth is sometimes involved. When it's overfed, just pumping the gill may not be giving the fish enough oxygen so it needs to pump more by adding mouth movement as well.
If the fish's " bloat" goes down after not eating for some time, it's not eggs or actual " bloat" that is causing this so the only likely cause is too much food. Because this is a community tank, I would suggest feeding the fish less food per feeding but feed more often. Try distracting this fish on one side of the tank while you feed the other fish from the other side of the tank. If the fish can digest what's eaten before the next feeding, that should help keep the fish from gorging itself or appearing extra full.
Hope this helps
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