Hi Opcn
I'm glad that you posted about your corys. I had been wondering how they were doing.
What you are describing sounds like the corys have spawned for you. Did they get a chill when they were being transported or when you added them to the tank?
They are not egg scatterers but rather they place their eggs on the glass or other surfaces. The corys will clean the eggs and remove any that are infertile or have gone bad. You can expect them to hatch in around 4 days from the time they were laid, so if you want to save them, be sure they have good water circulation around them and remove them to a safe place before that time. If not, you could move the corys and feed them live or frozen blackworms or bloodworms, and they will most likely spawn again in a couple of weeks.
Here's a link to a thread with pictures of cory eggs:
http/www.fishforums.net/index.php?showto...=0&#entry600033
Now, here's the problem. Corys are not territorial an will normally roam all around the tank. If they are staying in one place, it's not a good sign. The one with the damaged fins might have been bitten or it might have finrot. This should always be suspected when you first get them because of the stressful conditions they go through while being shipped around.
Bacterial infections (finrot) are the most common disease that corys get, and they will die from it if it is not treated. I suggest that you catch the sick one and move him, and the others too, to a hospital tank where they can be medicated and recover.
Either that, or he is being attacked by one of the fish and it will probably continue until he is dead. Please do something quickly.