09-03-2012, 08:13 PM
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Most tetra, being characins, are egg scatterers. If the females are ready, the males will chase them and drive one into a thicket of plants. The eggs are expelled and fertilized, and fall among the plants. Being sticky, they adhere to the leaves. The fish in the aquarium, recognizing what is going on, will usually then devour the eggs as fast as they are expelled. The parents too, when their spawning frenzy is finished, will readily eat any eggs they find.
What you describe would seem to be some health issue. I won't even try to guess what. Monitor the fish's behaviours, and check for any obvious signs of causes. A partial water change often helps.