I recently added a royal gramma and a cardinal into my tank. But now I have a dead royal beauty and now a Scarlet Skunk Cleaner Shrimp. My tank is 30 gallons and I only have 3 clown and a yellow tang as of now. Plus a few coral. Who's doing the killing? I had no fish deaths until I added these two. I see the gramma eating but not the cardinal. Is it reasonable to believe the cardinal is the cause ?