I just got 10 RCS a few days ago and now they are dying left and right. They were really costly and I don't want to lose my last 5 or 6. I did do a water change in case of something in the water this morning and did tests (everything's fine). The water doesn't have any chemicals in it, the tank's cycled too, and my 2-4 day old cory fry in there are very healthy. Any last minute ideas as how to save them?